Protagonist found woman's ring (4)
I believe the answer is:
hero
'protagonist' is the definition.
(I've seen this before)
'woman's ring' is the wordplay.
'woman' becomes 'her' (her refers to a woman).
'ring' becomes 'O' (O is the shape of a ring).
'her'+'o'='HERO'
'found' is the link.
(Other definitions for hero that I've seen before include "Man admired for courage and nobility" , "Exemplar" , "Brave guy" , "Book's chief character" , "Chief good guy in a story" .)