If the obelisk will detach, plant it with its current obelisk. This winter, prune it back to a couple of buds per stem and then remove the old trellis and replace it with a new larger one sized for the plant's eventual size. Newly planted clematis do better if hard pruned the first year or two. Also, clematis prefer being planted a few inches deeper than they were in the pot.

If it doesn't detach, clip the clematis away from the obelisk as best you can. I imagine that it is still quite a while until frost for you and it may grow some more this season or it may wait until next season. Depending, you may lose a few flowers next year, but it won't hurt the plant.

The obelisk can be removed from the pot so I will do that. Thanks for the information.