Posted: 11/06/2013 at 09:24
Looking at the flower in the bottom of the pot, it looks like maybe a Julia Correvon, which is a Viticella Clematis. These are very resistant to clematis wilt, plus wilt tends to turn the leaves black/brown more gradually than it sounds in your case. It could be another variety altogether of course!
As Wintersong says, get some pebbles in the pot to shade the root ball, and as it needs some extra tlc, I might be tempted to get some extra protection around the pot too, maybe lean something against the pot on each side to give the roots some extra shade.
I think it may have been the original shady spot which was the culprit here. If it's okay at the top and flowering, I would leave it. Make sure you cut it down to 6-8 inches in February time to get a good display next year.