Little width in very informal trousers (5)

I believe the answer is:

trews

I'm a little stuck... Click here to teach me more about this clue!

'trousers' is the definition.
(trews is a kind of trousers)

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

(Other definitions for trews that I've seen before include "Item of clothing" , "nether garments" , "close-fitting garments" , "Close-fitting tartan trousers" , "Garment" .)

I've seen this clue in The Sunday Times and The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.