This rogue's reformed, just! (9)
I believe the answer is:
righteous
'just' is the definition.
(associated in meaning)
'this rogue's reformed' is the wordplay.
'reformed' indicates an anagram.
'this'+'rogue'='thisrogue'
'thisrogue' anagrammed gives 'RIGHTEOUS'.
(Other definitions for righteous that I've seen before include "law-abiding" , "Morally justified" , "Showing virtue" , "Good!" , "Virtuous, free from sin or guilt" .)