Twelve back-to-back refusals (4)

I believe the answer is:

noon

'twelve' is the definition.
(twelve noon)

I cannot understand how the remainder of the clue works.

(Other definitions for noon that I've seen before include "when only mad dogs go out?" , "when PM starts" , "Twelve o'clock, midday" , "The middle of the day" , "12 o'clock" .)

I've seen this clue in The Times.

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