Boisterous fun (4,5)
I believe the answer is:
high jinks
'boisterous fun' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for high jinks that I've seen before include "Lively enjoyment" , "Boisterous fun" , "Boisterous behaviour" , "Noisy and mischievous merrymaking" , "You get horseplay" .)