A mundane subject (9)

I believe the answer is:

geography

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'subject' is the definition.
(geography is a kind of subject)

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

(Other definitions for geography that I've seen before include "15 down subject" , "Scientific study of earth's surface" , "The study of the earth" , "World study" , "school subject" .)

I've seen this clue in The Globe and Mail.

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