Well-behaved soldier (7)
I believe the answer is:
orderly
I believe this is a double definition.
'well-behaved' is the first definition.
(thesaurus)
'soldier' is the second definition.
(orderly is a kind of soldier)
(Other definitions for orderly that I've seen before include "Officer's assistant" , "Tidy officer's attendant" , "Junior Army rank" , "Hospital attendant - neat" , "Neatly arranged; hospital attendant" .)