Hi Nsoul, welcome to GoY, More info required about what type of Clematis. These plants are divided into different zones that all have their individual pruning requirements.

Basically it will depend on whether the clematis is an early or late season flowerer.

spring flowering = light prune immediately after flowering

summer flowering = light prune early spring

varieties which flower in late summer or autumn can be hard pruned in early spring to within a few inches of last years growth.

Spitzhenry did a great blog on 9th June 2009 describing exactly what to do when.