Owed money for prearranged fight (4)
I believe the answer is:
duel
'prearranged fight' is the definition.
(I've seen this before)
'owed money' is the wordplay.
'owed' becomes 'due' ('due' can be a synonym of 'owed').
'money' becomes 'l' (L can mean 'pounds').
'due'+'l'='DUEL'
'for' acts as a link.
(Other definitions for duel that I've seen before include "Fight between two people over an affair of honour" , "Two-person combat" , "honourable affair" , "Contest to settle point of honour" , "Contest between two people, perhaps with weapons" .)