Treat unjustly twice? That can't be right (6)
I believe the answer is:
wrongs
'can't be right' is the definition.
I can't tell whether this defines the answer.
'treat unjustly twice?' is the wordplay.
'treat unjustly' becomes 'wrong' (synonyms).
'twice?' becomes 's' (I can't justify this - if you can you should believe this answer much more).
'wrong'+'s'='WRONGS'
'that' is the link.
Can you help me to learn more?
(Other definitions for wrongs that I've seen before include "'Two ...... don't make a right'" , "Defrauds" .)