Banking head has responsibility to produce extra income (5)
I believe the answer is:
bonus
'extra income' is the definition.
(I've seen this before)
'banking head has responsibility' is the wordplay.
'head' suggests taking the first letters.
'has' is a charade indicator (letters next to each other).
'responsibility' becomes 'onus' (onus is a duty or responsibility).
The initial letter of 'banking' is 'b'.
'b'+'onus'='BONUS'
'to produce' acts as a link.
(Other definitions for bonus that I've seen before include "Extra money paid for good performance" , "- generis means unique" , "Extra payment for good work" , "Additional wage" , "Extra payment - reward" .)