Daybreak in Madrid (6)

I believe the answer is:

siesta

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'daybreak in madrid' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.

This is all the clue.

Can you help me to learn more?

(Other definitions for siesta that I've seen before include "After lunch nap" , "Seat is found for a Spanish rest period" , "PM snooze" , "Afternoon snooze" , "Spanish afternoon nap" .)

I've seen this clue in The Guardian.

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