Body of soldiers (5)
'body of soldiers' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for troop that I've seen before include "Military unit" , "Proto (anag.)" , "Gang" , "Group of, eg, monkeys" , "March" .)
(Other definitions for corps that I've seen before include "army band" , "Army unit" , "Branch of an army" , "Large army group" , "Military body" .)
'body of soldiers' is the definition.
This is all the clue.
(Other definitions for regiment that I've seen before include "Section of an army" , "Group of battalions" , "Military group" , "Force under colonel" , "Part of an army" .)