I saw your previous posts about this issue but didn't respond then as I have no idea what is causing this leaf deformation. It looks very much like herbicide/chemical damage IMO, but if you are certain nothing was applied/sprayed in that area and no other nearby plants affected, that would not seem to be the case.

In all my years of growing a huge array of various types of clematis, I have never encountered this sort of foliar growth before. I would be interested to see how the vine progresses during the season and if it outgrows this.

Sorry not to be of any help :-(

I feel the same. I have grown dozens of clematis over the years and never seen this. The vines that started this way, like the one in the picture, are not growing at all. Have looked just like this for a month and a half. I'm consulting the local extension service to see if they can identify this:(

I have a clematis doing this one one stem only. Weird.