Ludicrous or grotesque act (5)
I believe the answer is:
antic
I believe this clue is a double definition.
'ludicrous' is the first definition.
(I've seen this in another clue)
'grotesque act' is the second definition.
(I've seen this in another clue)
(Other definitions for antic that I've seen before include "Mad act done for fun" , "Grotesque, fantastic (archaic)" , "Old clown" , "Absurd act" , "Prank" .)