Owed pound in honourable affair (4)
I believe the answer is:
duel
'honourable affair' is the definition.
(I've seen this before)
'owed pound' is the wordplay.
'owed' becomes 'due' (synonyms).
'pound' becomes 'L' (abbreviation e.g. Lsd - pounds, shillings, pence).
'due'+'l'='DUEL'
'in' acts as a link.
(Other definitions for duel that I've seen before include "Combat between two people in matter of honour" , "One got satisfaction from this" , "Fight between two persons" , "honourable affair" , "Fight to the death between two people" .)