Not necessarily brownish attire (6)

I believe the answer is:

livery

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'not necessarily brownish attire' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I don't see?

This is all the clue.

Can you help me to learn more?

(Other definitions for livery that I've seen before include "Fancy dress for footmen" , "The stabling and care of horses" , "Feeding and stabling of horses for money" , "Uniform - commercial care of horses" , "Irritable" .)

I've seen this clue in the Evening Standard.

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