Get married after ring's due (4)
I believe the answer is:
owed
'due' is the definition.
('owed' can be a synonym of 'due')
'get married after ring's' is the wordplay.
'get married' becomes 'wed' ('wed' can be a synonym of 'get married').
'after' means one lot of letters go next to another.
'ring' becomes 'o'.
'wed' put after 'o' is 'OWED'.
(Other definitions for owed that I've seen before include "Had an obligation to pay" , "Outstanding" , "to be paid" , "(Sum) due for payment" , "Was obliged to pay" .)