Drill order applies mostly to those dressed in it (5)
I believe the answer is:
khaki
'drill' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for khaki that I've seen before include "Military uniform cloth - colour" , "Dull brown colour" , "Army uniform cloth" , "Army fabric" , "Drab military colour" .)