How the confounded light is going on and off? (8)

I believe the answer is:

blinking

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'off?' is the definition.
Both the answer and definition are adjectives. Perhaps you can see a link between them that I don't see?

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

Can you help me to learn more?

(Other definitions for blinking that I've seen before include "Quick closing and opening of the eyelid" , "Damned" , "response to grit in eye?" .)

I've seen this clue in the Evening Standard.

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