Latterday period (9)

I believe the answer is:

afternoon

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'period' is the definition.
(I know that afternoon is a time of the day)

I don't understand the remainder of the clue.

(Other definitions for afternoon that I've seen before include "Post-midday" , "half a day?" , "Then it's early in this!" , "Midday to evening" , "Time of day" .)

I've seen this clue in The Globe and Mail.

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