Amusing behaviour (6)
I believe the answer is:
antics
'amusing behaviour' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for antics that I've seen before include "'Capers, pranks (6)'" , "Clowning" , "extraordinary goings-on" , "Absurd or foolish movements intended to amuse" , "Movements intended to be amusing, pranks" .)