Military unit also included in scheme (7)
I believe the answer is:
platoon
'military unit' is the definition.
(platoon is a kind of military unit)
'also included in scheme' is the wordplay.
'also' becomes 'too' (synonyms).
'included in' indicates putting letters inside.
'scheme' becomes 'plan' (synonyms).
'too' placed inside 'plan' is 'PLATOON'.
(Other definitions for platoon that I've seen before include "Soldiers under lieutenant" , "Sub-unit of a military company" , "Military squad" , "Infantry unit" , "Army unit" .)