Where are you, generally? Can you take a photo of the leaf damage and post it? (You can use the choose file above the follow-up box in the line just below "Post a Follow-Up" to add a photo. To add more than one photo, do multiple follow-ups, changing the title each time.)

Around me, it could be rabbits or earwigs among other things, but my pests may not be the same as yours.

The rabbits eat my clematis (among other plants) that are low to the ground, once they've grown a few feet they decide to leave them alone. I've started wrapping chicken wire around the base of my clematis when they are young & that helps.

Good luck!

I've just ordered one to add to my clematis collection, don't think ther fully hardy over here in the UK

I don't grow this Clematis but I know I battle slugs constantly with new Clematis shoots. They will scrape them to stubs. Even if you can't see any I bet they're there just under the soil surface or under debris. I have just come in from a bit of tidying up and every ground hugging plant, e.g. Dianthus, has slugs under it. It is not too cold for them to be busy. They have already started chewing off the buds of various bulb flowers. They often destroy my snowdrop, hyacinth and daffodil flowers before they even open.