Also in scheme — group of soldiers (7)
I believe the answer is:
platoon
'group of soldiers' is the definition.
(type of military subdivision)
'also in scheme' is the wordplay.
'also' becomes 'too' (synonyms).
'in' means one lot of letters goes inside another.
'scheme' becomes 'plan' (synonyms).
'too' inserted inside 'plan' is 'PLATOON'.
(Other definitions for platoon that I've seen before include "Company's subdivision" , "Small military unit" , "Group under lieutenant" , "part of company" , "Team under lieutenant" .)