Costs incurred and claimed by people once married? (4)
I believe the answer is:
exes
'people once married?' is the definition.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for exes that I've seen before include "former union members" , "old dates" , "Expenses (abbrev.)" , "Reduced claim from employer" , "divorcees?" .)