It appears to be one of the several different leaf spots that can befall clematis. Most are more cosmetic than serious or damaging, but it's always a good idea to remove affected foliage/stems to prevent the spread. Typically, these are caused by moisture/high humidity and lack of good air circulation.

Hmm. So far humidity should not be a factor although if left over effect from last summer season -- perhaps. I think the air circulation is decent -- I will take your advice and get rid of as much of the affected leaves. Thanks very much.