Play in a prom, possibly (4)
I believe the answer is:
romp
'play' is the definition.
(synonyms)
'in a prom possibly' is the wordplay.
'in' indicates a hidden word.
'ROMP' is hidden within 'prom possibly'.
(Other definitions for romp that I've seen before include "Frisk - gambol" , "Make merry at prom" , "Cavort" , "Play boisterously" , "sexy fun" .)