Group of enthusiasts (3,4)
(Other definitions for fan club that I've seen before include "Devoted followers collectively" , "Keep place of entertainment cool" , "Admiration society" , "Admiring band" , "Fervent admirers" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">group of enthusiasts</span>' is the definition.<br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for fandom that I've seen before include "body of supporters" , "enthusiasm" , "Enthusiastically supportive followers" , "devotion" , "Devotees, collectively" .)