Being responsible, deduct billions from payout (4)
I believe the answer is:
onus
'being responsible' is the definition.
(the onus for something is being responsible for it)
'billions from payout' is the wordplay.
'billions' becomes 'b'.
'from' is a deletion indicator.
'payout' becomes 'bonus' (I have seen 'Extra payout' mean 'bonus' so perhaps 'payout' could also mean 'bonus').
'bonus' with 'b' taken away is 'ONUS'.
'deduct' is the link.
This may not be correct. It may belong to another bit of the clue.
(Other definitions for onus that I've seen before include "Obligation - charge" , "Capulet opponent (R&J)" , "Responsibilty" , "Duty or responsibility" , "'Responsibility, task or burden (4)'" .)