Shot back, mad (4)
I believe the answer is:
stab
'shot' is the definition.
(I know that shot can be written as stab)
'back mad' is the wordplay.
'back' says the letters should be written in reverse.
'mad' becomes 'bats' (informal term for mad).
'bats' written backwards gives 'STAB'.
(Other definitions for stab that I've seen before include "Go" , "Puncture" , "Strike with knife" , "Wound with blade" , "Run through - essay" .)