I'd just leave it alone now to do its thing and replace the trellis next season after you prune the vine. It'll just be a low clematis "shrub" this year :-)

Now might be the time to buy the trellis or obelisk so it reminds you this fall, winter, or early spring to set it out for next season and to prune the clematis. I leave my trellises out year round and usually decorate some with lights for the winter.

Michael I have a trellis but neglected to train the vines as well. So mine are in a ball too and the vines are too soft and fragile to untangle. I guess I should just leave mine alone this season too.

They don't climb wood very well, much better to use thinner wire or even rebar trellises. After they bloom you can cut them back and replace or wait until next year. Trying to untangle carefully is a lesson in frustration.

This happened to me too this year with a new Clem that took off faster than I expected. My nursery has expanding willow triangular trellises for about $8. They have a large base and I stuck it over the whole plant so at least new shoots have somewhere to go.