Pay wife to decline (4)
I believe the answer is:
wage
'pay' is the definition.
(I know that pay can be written as wage)
'wife to decline' is the wordplay.
'wife' becomes 'w'.
'to decline' becomes 'age' (I've seen this in other clues).
'w'+'age'='WAGE'
(Other definitions for wage that I've seen before include "Regular payment for work" , "Salary" , "Amount earned" , "Engage in (war?)" , "Regular amount of income" .)