How do I leave a club?

From the club's page, leave it. Your posts and comments stay where they are — leaving removes your membership, not your contributions — and you can re-join later unless the club requires approval, in which case you go through that again.

Your member level and score in that club are tied to the membership, so leaving and re-joining starts your tenure over even though your posts remain.

If you are the club owner, you cannot simply leave: the club needs an owner. Hand ownership over or delete the club instead.