Blooming mid- to late summer would indicate a pruning group 3 or hard-prune clematis. These bloom on new growth each season and should be cut back to the third set of buds from the ground annually in late winter. It's getting a little late but prune it now. It will clean things up and at worst, it might delay the bloom period slightly.

FWIW, all clematis types benefit from hard pruning for their first couple of seasons in the ground. And while pruning guidelines are just that - guidelines - I've yet to see pruning group 3 clem that didn't look (and bloom) better after a good hard prune. Otherwise, they just end up a mess of tangled dead vines with some green at the top.

Thanks