You can leave any club from My Clubs in your account settings. What happens next depends on your role there:
- Not the sole Owner: leaving is immediate. Just confirm and you're out.
- Sole Owner, with other members still in the club: you'll need to transfer ownership to someone else first (see Transferring club ownership) before you can leave, because a club can never be left without an owner.
- Sole Owner and the only remaining member: leaving deletes the club entirely. The confirmation screen spells this out explicitly before you go ahead, so it's never a surprise.