High-flying singer’s frolic (4)
I believe the answer is:
lark
This clue is a double definition.
'high-flying singer's' is the first definition.
(songbird)
'frolic' is the second definition.
(I know that frolic can be written as lark)
(Other definitions for lark that I've seen before include "Songbird - bit of fun" , "Game - bird" , "Early bird with morning song" , "Songbird; escapade" , "One singing high" .)