Do something for Bill, eventually? (3)
I believe the answer is:
act
This clue is a double definition.
'do something' is the first definition.
(to act is to do something)
'bill eventually?' is the second definition.
(eg a bill becomes an Act of Parliament)
'for' is the link.
(Other definitions for act that I've seen before include "Produce an effect" , "Play (a role)" , "Start of a drama" , "Take part in a play" , "Feat" .)