Disprove a brute has been converted (5)
I believe the answer is:
rebut
'disprove' is the definition.
(rebutting is a kind of disproving)
'a brute has been converted' is the wordplay.
'brute' can be anagrammed to 'REBUT'.
However, I am not sure how this is indicated.
Can you help me to learn more?
(Other definitions for rebut that I've seen before include "Overthrow by argument or proof" , "Give the lie to" , "Confute" , "Prove to be false or incorrect" , "Prove (something) to be false" .)