Married type's exploit (4)
I believe the answer is:
milk
'exploit' is the definition.
(to milk something is to exploit its potential)
'married type's' is the wordplay.
'married' becomes 'm'.
'type' becomes 'ilk' (ilk can mean a type or kind).
'm'+'ilk'='MILK'
(Other definitions for milk that I've seen before include "White liquid" , "A white drink" , "Exploit" , "Extract money from" , "Nourishing fluid produced by mammals" .)