Don't agree it's been broken through stupidity (7)

I believe the answer is:

density

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'stupidity' is the definition.
(thesaurus)

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

(Other definitions for density that I've seen before include "Bulk" , "Concentrated condition as of fog" , "showing obtuseness" , "Degree of compactness" , "can be relative" .)

I've seen this clue in the Evening Standard.

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