Primarily bear responsibility for extra dividend (5)
I believe the answer is:
bonus
'extra dividend' is the definition.
(I've seen this before)
'primarily bear responsibility' is the wordplay.
'primarily' says to take the initial letters.
'responsibility' becomes 'onus' (I've seen this before).
The first letter of 'bear' is 'b'.
'b'+'onus'='BONUS'
'for' is the link.
(Other definitions for bonus that I've seen before include "Tip" , "bribe" , "Extra money paid on top of salary" , "Additional payment for work, often on merit" , "Perk" .)