Being villainous, use no fair play (9)
I believe the answer is:
nefarious
'being villainous' is the definition.
(synonyms)
'use no fair play' is the wordplay.
'play' indicates an anagram.
'use'+'no'+'fair'='usenofair'
'usenofair' is an anagram of 'NEFARIOUS'.
(Other definitions for nefarious that I've seen before include "immoral?" , "Very bad" , "Extremely wicked" , "Villainous" , "Wicked, criminal" .)