Crossword Genius

Drill order applies mostly to those dressed in it (5)

Ross

I believe the answer is:

khaki

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'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" .)

I've seen this clue in the Sydney Morning Herald.
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