Foremost of shorts-wearers doesn't own trousers (6)

I believe the answer is:

slacks

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'trousers' is the definition.
(type of trousers)

I don't understand the remainder of the clue.

(Other definitions for slacks that I've seen before include "Works lazily; trousers" , "casual attire" , "Things to wear" , "bags" , "Loose casual trousers" .)

I've seen this clue in The Independent.

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