Cruel don’s going badly rogue (9)
I believe the answer is:
scoundrel
'rogue' is the definition.
(both can mean a dishonourable person)
'cruel don's going badly' is the wordplay.
'going badly' indicates an anagram.
'cruel'+'dons'='crueldons'
'crueldons' anagrammed gives 'SCOUNDREL'.
(Other definitions for scoundrel that I've seen before include "Disreputable type" , "Hound" , "Bounder" , "Villain" , "Untrustworthy figure" .)