Acknowledge deferred payment (6)
I believe the answer is:
credit
I believe this clue is a double definition.
'acknowledge' is the first definition.
(I've seen this in another clue)
'deferred payment' is the second definition.
(synonyms)
(Other definitions for credit that I've seen before include "Due recognition for kind of loan?" , "Put down" , "Belief; tick" , "Add (an amount) to an account" , "Acknowledgment, recognition or praise" .)