Playing roles one hasn't won (5)
I believe the answer is:
loser
'one hasn't won' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'playing roles' is the wordplay.
'playing' indicates an anagram.
'roles' anagrammed gives 'LOSER'.
Can you help me to learn more?
(Other definitions for loser that I've seen before include "lemon" , "A failure, also-ran" , "Failed competitor" , "Unsuccessful competitor" , "One who regularly fails" .)