Crossword Genius

Fairground ride is to revert to previous state (10)

Ross

I believe the answer is:

switchback

I believe this is a double definition.

'fairground ride' is the first definition.
(switchback can mean a roller coaster)

'revert to previous state' is the second definition.
(to switch back to an earlier state)

'is to' acts as a link.

(Other definitions for switchback that I've seen before include "uneven way" , "Up-and-down road" , "fairground attraction" , "ups and downs" , "big dipper" .)

I've seen this clue in The Times.
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