What would you do with this clematis?

[Mykittensmittens]

It’s growing over an archway, it was here when we moved. It’s flowers spectacularly in early June.

but it’s very tangled up with lots of brown bits which look bad now, but worse by January.

I feel inclined to give it a bit prune, assuming it’s group 2? Is it okay to do this or will I kill it? If I prune, how ruthless should I be? I don’t want to loose it!

thanks

You are unlikely to kill it by pruning, if you prune too much you are just likely to lose some of the flowers next year.