Paid work? (4)
I believe the answer is:
duty
'work?' is the definition.
(duty is a kind of work)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for duty that I've seen before include "A tax; compulsory task" , "Financial or work obligation" , "Task; military service" , "Kind of obligation or tax" , "Service - tax - office" .)