Military unit also into strategy (7)
I believe the answer is:
platoon
'military unit' is the definition.
(platoon is a kind of military unit)
'also into strategy' is the wordplay.
'also' becomes 'too' ('too' can be a synonym of 'also').
'into' indicates putting letters inside.
'strategy' becomes 'plan' (I've seen this before).
'too' inserted into 'plan' is 'PLATOON'.
(Other definitions for platoon that I've seen before include "detail" , "Company's subdivision" , "Small body of soldiers" , "Soldiers under lieutenant" , "Military squad" .)