Voucher for money owed (4)
I believe the answer is:
chit
'voucher for money owed' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for chit that I've seen before include "Short official note recording a sum owed" , "Pert young lady" , "struck" , "Docket; pert girl" , "Impudent youngster" .)