Relief after penny spent (4)
I believe the answer is:
paid
'spent' is the definition.
(thesaurus)
'relief after penny' is the wordplay.
'relief' becomes 'aid' (I've seen this before).
'after' is a charade indicator (letters next to each other).
'penny' becomes 'p' (short for pence).
'aid' put after 'p' is 'PAID'.
(Other definitions for paid that I've seen before include "Trite phrase" , "Hired" , "Settled the bill" , "Forked out" , "Gave money for goods or services" .)