Off the top of my head I couldn't recall anyone... Though I'm sure there is one or two... damn TVTropes has monster clowns, but no one with fears of them... Though, to be fair, if you have a monster clown in your series/game, chances are you are spooked by them, so there's a place to start from. If anyone actually has it, that would probably be more desirable.
http://tvtropes.org/pmwiki/pmwiki.php/Main/MonsterClown
http://tvtropes.org/pmwiki/pmwiki.php/Main/CircusOfFear