Noncommissioned officer (8)
I believe the answer is:
sergeant
'noncommissioned officer' is the definition.
(I know that sergeant is a type of noncommissioned officer)
This is all the clue.
(Other definitions for sergeant that I've seen before include "Police rank" , "NCO or police officer ..." , "Estrange from junior army officer" , "Rank above corporal" , "NCO; Death a fell one, Hamlet" .)