Attack Bill's ward (6)
I believe the answer is:
charge
I believe this is a triple definition!
'attack' is the first definition.
(I know that attack can be written as charge)
'bill's' is the second definition.
(synonyms)
'ward' is the third definition.
(both can mean a child in someone's care)
(Other definitions for charge that I've seen before include "Accuse of a crime" , "Be aggressive" , "Fill; fee" , "Price asked; fill" , "Move quickly and violently" .)