Head-to-toe cover for garment? (5)

I believe the answer is:

trews

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'garment?' is the definition.
(trews is a kind of garment)

I don't understand how the rest of the clue works.

(Other definitions for trews that I've seen before include "Close-fitting tartan trousers" , "Trousers of a Scot" , "nether garments" , "Some clothes" , "Wrest (anag) - trousers" .)

I've seen this clue in The Telegraph.

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