From the TH, the trail climbs east uphill, passes through a gate (please keep closed) and turns south and climbs steadily gaining about 200 feet before leveling out and contouring above the ranch property. This is trail #1975 on the White River Forest Service map. A little over a mile in, (perhaps 1.5) it intersects another trail which leads down to Snowmass Creek where one can wade across to access the West Snowmass Creek trail, fairly easy to spot heading off across an open field and into a stand of aspen.
Continue along the main trail south from this intersection. From the TH, hike an overall distance of about 3 miles to where you may see a cairn or cairns and a possible crossing of Snowmass Creek. If you reach a place where the main trail begins to ascend steeply, you've gone too far. The crossing of Snowmass Creek is also about a half mile before where Copper Creek comes in. At the crossing point, the main trail comes very close to the creek.
Note: Ryan Schilling notes on SummitPost in 2004 a "makeshift" log bridge with handrail across the creek in this area. In 1993 and again in 2013, we never saw this. It may be further upstream than the crossing we are suggesting here. Check out his description on SummitPost for yourself. Also, a report passed on to us by Amy Johnstone said that you'll only find this log crossing if you go "too far," then backtrack down the hill some in order to spy it. She describes it as "a distinctive camp along Snowmass Creek right before you start the little climb and not far at all from Copper Creek (about 500 yards downstream)."
The climbing route begins with the crossing of Snowmass Creek, which may in itself be quite an adventure in the earlier season. There can be a powerful flow here when the runoff is still going. Later season will be easier crossing. Once across, search for a somewhat faint trail heading south. In about 15 minutes, you'll come to the crossing of Copper Creek. The trail can be very sketchy here in the tall vegetation & willows. Beyond Copper Creek, continue south for about 3/4 mile and then the trail will begin to turn more to the SW as it heads up the Bear Creek drainage. Soon, the waterfall section of Bear Creek will come into view. You'll have to cross a talus/boulder field where we found maybe two cairns in our 2013 trip through here. Stay at all times on the north side of the creek. After the talus/boulder field, the trail will avoid the falls by heading up through low aspen, willows, rocks and minor cliffbands taking you away from the creek as it ascends steeply. At 10,400, it will begin to level out some. If you've lost the trail coming up, you may find it again around here. At 10,600, there will be a good campsite, not far from the head of some falls.
Above 10,600 ft., continue on the vague trail as it heads up through the forest and begins to climb steeply again just above 10,800 ft. Walk up through more open forest to the last trees where you'll finally have a view of Clark. Turn to a NW direction and aim for the broad SSE ridge coming off Clark. Our route took us between the two smaller lakes at the foot of that ridge.
From the lakes, head up the broad SSE ridge on easier rock or gentle snowfields until you come to a cliffband at about 12,600 ft. We climbed a little to the left of the ridge on large rocks, ledges and tundra to get through the cliffs. Prior to the cliffs, you may encounter large, stacked & teetering boulders. It was 3rd class scrambling at points. Once beyond the cliff, we continued on the broad SSE facing ridge/slope with a more gentle gradient and some tundra, but mostly small scree and rocks which gave way to an increasing number of large, teetering boulders as we hiked higher. The last 300 feet to the summit consisted mostly of these teetering boulders that required considerable rock-hopping, clambering up, down and over and great care taken to not step on one of the teetering blocks and have it roll onto your leg. One fellow-peakbagger reported to us in 2015 that if you bear left as far as you can while approaching the summit, you can avoid some of the teetering rocks by walking on more stable talus.
Once on the summit, breathe a sigh of relief if you've made it without injury and then remind yourself that you still have to cover all that terrain again and the bushwhack to get back down by the same return route. Maybe you'll have more luck following the trail back down. If there are snowfields along the ridge going back down, bring an ice axe and enjoy a glissade for several hundred feet. The Snowmass Creek trail will seem like a welcome, interstate highway when you finally get back to it.
Count on a 12 hour day to do this one. This is a real foot-burner.
Extra Credit: If you're even thinking about climbing all the 13ers, the ESE ridge of Clark leads over a low 13er: UN 13,060. We call it, UN13SOB. It would be a good idea for all the effort you've invested, to bag this one too, but the traverse over will be difficult and at least 4th class. East of the UN 13,060 summit, there is a saddle that has two large couloirs descending either north or south. 1,800 feet of endless rubble and boulder hopping down the south one will bring you back to the so-called Pierre Lakes trail for your exit. If you don't want to do this one with Clark, see our route description for UN13,060 alone.
Links to other information, routes & trip reports for this peak that may be helpful.