Fight to get proper money (4)
I believe the answer is:
duel
'fight' is the definition.
(I know that duel is a type of fight)
'get proper money' is the wordplay.
'get' says to put letters next to each other.
'proper' becomes 'due' (what is due is what is proper or appropriate).
'money' becomes 'l' (L can mean 'pounds').
'due' put next to 'l' is 'DUEL'.
'to' acts as a link.
(Other definitions for duel that I've seen before include "Combat to settle a row" , "battle" , "Single combat" , "Fight to the death between two people" , "Fight between two persons" .)