Flipping go mad (4)
I believe the answer is:
bats
'mad' is the definition.
(informal term for mad)
'flipping go' is the wordplay.
'flipping' shows that the letters should be reversed in order.
'go' becomes 'stab' (both can mean an attempt).
'stab' back-to-front is 'BATS'.
(Other definitions for bats that I've seen before include "Mad - clubs" , "Cuckoo" , "Hits" , "Night-flying creatures" , "Mad; mammals" .)