Attack is in good shape (3)
I believe the answer is:
fit
I believe this is a double definition.
'attack' is the first definition.
(I know that fit is a type of attack)
'in good shape' is the second definition.
(I've seen this in another clue)
'is' acts as a link.
(Other definitions for fit that I've seen before include "Suitable; healthy" , "Equip" , "Able-bodied" , "Apt" , "Adapt; well" .)