Affaire d'honneur (4)
I believe the answer is:
duel
'affaire d'honneur' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for duel that I've seen before include "Combat to settle a row" , "Single combat" , "Contest between two with deadly weapons" , "Prearranged fight with deadly weapons between two people" , "honourable affair" .)