Kind of lacey, grey-green foliage? Probably one of the cartmanii hybrids. This plant is a bit tender outdoors even in our climate, but I've never encountered anyone that had much success with any clematis indoors long term. Any type of water soluble fertilizer suitable for flowering house plants should work - Schultz, Peters and Miracle Gro all make appropriate formulations. Wait util the plant is pushing new growth before applying. And you will most likely need to reapply periodically through the growing season. Containerized plants of any kind need regular supplements of necessary nutrients that are leached out with frequent watering.

These leaves are actually rather shiny. Also, this particular clematis is incredibly hardy outside-it withstands our frosts and freezes without losing a leaf, generally. Also, I have 2 starts inside, one of which needs some help, but the other is doing incredibly well-growing upwards of 8 or 9 feet or so (so far).
There is a garden-variety clover that has made its way into the pot of the sickly clematis. I suspect this may have something to do with its 'pekidness'.
Thanks