Pursue wife over a number of years (4)
I believe the answer is:
wage
'pursue' is the definition.
(I've seen this before)
'wife over a number of years' is the wordplay.
'wife' becomes 'w'.
'over' is a charade indicator (letters next to each other).
'a number of years' becomes 'age' (I've seen this in other clues).
'w'+'age'='WAGE'
(Other definitions for wage that I've seen before include "Earnings - carry on" , "Money paid to worker" , "Regular pay" , "Engage in (war?)" , "Pay (enough to live on?)" .)