An awkward brute to disprove (5)
I believe the answer is:
rebut
'disprove' is the definition.
(I know that rebut is a type of disprove)
'an awkward brute' is the wordplay.
'an awkward' indicates anagramming the letters.
'brute' anagrammed gives 'REBUT'.
'to' acts as a link.
(Other definitions for rebut that I've seen before include "Claim or prove to be false" , "Brute can refute" , "Prove the claim wrong" , "Drive back" , "Overturn" .)