Buffoonery (6)
I believe the answer is:
antics
'buffoonery' is the definition.
(both can mean silly behaviour)
This is all the clue.
(Other definitions for antics that I've seen before include "Cat's in (anag.)" , "Absurd behaviour intended to amuse" , "Tomfoolery" , "Buffoonery" , "Clowning" .)