One who failed to win new roles (5)
I believe the answer is:
loser
'one who failed to win' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'new roles' is the wordplay.
'new' indicates an anagram.
'roles' anagrammed gives 'LOSER'.
Can you help me to learn more?
(Other definitions for loser that I've seen before include "Roles for the defeated" , "Proverbially, one who hesitates" , "Unsuccessful competitor" , "Ineffectual person who regularly fails" , "Failed competitor" .)