Pounds added to independent working payment (7)
I believe the answer is:
pension
'payment' is the definition.
(pension is a kind of payment)
'pounds added to independent working' is the wordplay.
'pounds' becomes 'pens'.
'added to' says to put letters next to each other.
'independent' becomes 'i'.
'working' becomes 'on'.
'pens'+'i'+'on'='PENSION'
(Other definitions for pension that I've seen before include "Income in retirement" , "Retirement allowance" , "Retired person's allowance" , "Retirement pay in a Continental boarding-house" , "what oldies may have earned" .)