Uncle Rod's turned out to be a villain (9)
I believe the answer is:
scoundrel
'a villain' is the definition.
('scoundrel' can be a synonym of 'villain')
'uncle rod's turned out' is the wordplay.
'turned out' is an anagram indicator.
'uncle'+'rods'='unclerods'
'unclerods' is an anagram of 'SCOUNDREL'.
'to be' acts as a link.
(Other definitions for scoundrel that I've seen before include "Knave" , "bad egg" , "Rascal" , "Person that's low" , "Untrustworthy figure" .)