Posted: 01/03/2014 at 18:11
Have you planted it several inches deeper than it was in its pot? This helps encourage extra shoots from the roots and makes for a strudier plant.
Clematis can take a couple of years to settle in before they really get going so, unless it's an early spring flowering variety and group 1 for pruning, I would prune it back to just above those buds and give it a good feed of proprietary clematis food plus a drink of liquid tomato food to help it along. This will let it put its energy into good root formation which will pay dividends in future years for extra top growth and flowers.