Fun at dance? (4)
I believe the answer is:
ball
I believe this is a double definition.
'fun' is the first definition.
(thesaurus)
'dance?' is the second definition.
(ball is a kind of dance)
'at' acts as a link.
(Other definitions for ball that I've seen before include "Spherical object" , "Sphere - dance" , "Spherical plaything" , "that one might throw?" , "20" .)