Direct change in time allowed for payment (6)
I believe the answer is:
credit
'time allowed for payment' is the definition.
(I've seen this before)
'direct change' is the wordplay.
'change' indicates an anagram.
'direct' with letters rearranged gives 'CREDIT'.
'in' acts as a link.
(Other definitions for credit that I've seen before include "Believe - recognition" , "Time given to pay for goods" , "Add (money) to account" , "Opposite of debit" , "Believe; acknowledgement" .)