Endorsed boxer courted after victory (9)
I believe the answer is:
validated
'endorsed' is the definition.
(thesaurus)
'boxer courted after victory' is the wordplay.
'boxer' becomes 'Ali' (Muhammad Ali).
'courted' becomes 'dated' (romantically pursued).
'after' means one lot of letters go next to another.
'victory' becomes 'v'.
'ali'+'dated'='alidated'
'alidated' after 'v' is 'VALIDATED'.
(Other definitions for validated that I've seen before include "certified" , "backed up" , "proved true" .)