I have taken cuttings of several clematis just the last couple of days. Look for the sturdy,new shoots which at the moment are growing away quite fast.
,without any flowers on them. I am a novice but am having some success with using the propagator for lower warmth.
The new growth ( not woody),seems to be the best part to use at this time of the year.
I know there are a lot of far more experienced people than myself who can help you more,but so far ,no one else has replied .You could try asking google 'How to grow clematis',

Thank you Vera, i didn't think I was going to get a reply on this question.I will do it tomorrow,I don't know the name, as it's coming over my fence at the bottom of my garden. aren't I naughty ??