An adversity? Quite otherwise (7)

I believe the answer is:

reverse

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'an adversity?' is the definition.
(thesaurus)

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

(Other definitions for reverse that I've seen before include "Invert" , "Travel backwards" , "come back" , "Turn inside out or upside down" , "Back (of a coin or medal)" .)

I've seen this clue in the Evening Standard.

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