Into battle - that's extreme (4-3-3)
I believe the answer is:
over-the-top
This clue is a double definition.
'into battle' is the first definition.
(I've seen this before)
'extreme' is the second definition.
(I've seen this before)
'that's' is the link.
(Other definitions for over-the-top that I've seen before include "To an exaggerated degree" , "Theatrically excessive" , "Excessively extreme" .)