In the lower right hand corner in "My clubs", click the link that says, "more clubs >>>"
It will show you a list of all your clubs and under the club's name is "unsubscribe". Click it.
Go on your profile and click on 'clubs'. There will be a list of every club you are in. Find the club you want to leave and click 'unsubscribe'. I will ask you if you're sure so click 'yes'. That should help.
In the top right hand corner it says 'search Fanpop', search the club and click on it. Once on the club scroll down a little and it should say 'unsubscribe', click that. Hope that helps :)