More straight trousers lost — SOS sent out (5)

I believe the answer is:

truer

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'more straight' is the definition.
('true' can be a synonym of 'straight')

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for truer that I've seen before include "More exact" , "That's more like it" , "More accurate" , "More faithful or straight" , "More relaible" .)

I've seen this clue in The Guardian.

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