Attack bill (6)
I believe the answer is:
charge
This clue is a double definition.
'attack' is the first definition.
(I've seen this before)
'bill' is the second definition.
('charge' can be a synonym of 'bill')
(Other definitions for charge that I've seen before include "Set price or mount onslaught" , "Attack - require payment" , "responsibility" , "Formal accusation" , "Accuse or rush forward" .)