One of the fabrics a drill sergeant possesses (5)

I believe the answer is:

serge

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'one' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.

I can't explain the remainder of the clue.

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(Other definitions for serge that I've seen before include "Material to suit" , "Strong twilled worsted fabric" , "Durable fabric" , "Twilled fabric; name" , "Frenchman" .)

I've seen this clue in the Evening Standard.

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