After a year, year's income (3)
I believe the answer is:
pay
'income' is the definition.
(income from a job)
'after a year year's' is the wordplay.
'after' says to put letters next to each other.
'a year' becomes 'pa' (per annum).
'year' becomes 'y'.
'pa' next to 'y' is 'PAY'.
(Other definitions for pay that I've seen before include "Give money in exchange for goods or services" , "Be punished" , "Profit" , "Money for work" , "Settle up" .)