"Have fun!" (5)
I believe the answer is:
enjoy
'have fun' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for enjoy that I've seen before include "Have the benefit of" , "Savour - relish" , "Fancy" , "-- Out means to fall heavily asleep (Z, not C)" , "Take pleasure in" .)