A dirty globe? (5)

I believe the answer is:

earth

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'globe?' is the definition.
('Earth' can be a synonym of 'globe')

I don't understand the remainder of the clue.

(Other definitions for earth that I've seen before include "Our favourite planet" , "Human world" , "Heart (anag)" , "Mud" , "Fox's burrow" .)

I've seen this clue in the Evening Standard.

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