Deranged like a door with nothing to swing on (8)

I believe the answer is:

unhinged

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'deranged' is the definition.
('unhinge' can be a synonym of 'derange')

I cannot understand how the remainder of the clue works.

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(Other definitions for unhinged that I've seen before include "[NUTTY]" , "characteristic of door after dislodgement?" , "Mentally unbalanced like defective door?" , "Mad - hen dug in (anag)" , "Wild" .)

I've seen this clue in the Sydney Morning Herald.

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