A failure in new roles (5)
I believe the answer is:
loser
'a failure' is the definition.
(someone who has failed)
'new roles' is the wordplay.
'new' is an anagram indicator.
'roles' anagrammed gives 'LOSER'.
'in' is the link.
(Other definitions for loser that I've seen before include "One who is (always) unsuccessful" , "sad type?" , "One vanquished" , "Defeated person" , "Roles for a non-winner" .)