This writer's in stupid short trousers (6)

I believe the answer is:

denims

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But I can't explain it at all! Could you help me understand?

(Other definitions for denims that I've seen before include "Clothes made of strong twilled cotton fabric" , "hard-wearing trousers" , "Jeans" , "Hard-wearing clothes for work or play" .)

I've seen this clue in The Times.

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