Uncle Rod's terrible cad (9)
I believe the answer is:
scoundrel
'cad' is the definition.
(thesaurus)
'uncle rod's terrible' is the wordplay.
'terrible' is an anagram indicator.
'uncle'+'rods'='unclerods'
'unclerods' with letters rearranged gives 'SCOUNDREL'.
(Other definitions for scoundrel that I've seen before include "A rogue or dishonest person" , "Untrustworthy figure" , "Rascal" , "Rat" , "Cad" .)