Deny being a crazy brute! (5)
I believe the answer is:
rebut
'deny' is the definition.
(to rebut is to deny or refute)
'a crazy brute' is the wordplay.
'a crazy' indicates anagramming the letters.
'brute' is an anagram of 'REBUT'.
'being' acts as a link.
(Other definitions for rebut that I've seen before include "Give the lie to" , "Overthrow by argument or proof" , "Overturn" , "Brute can refute" , "Prove to be false or incorrect" .)