Quiet hours? Why not seconds? (4)

I believe the answer is:

hush

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'quiet' is the definition.
(hush can mean still or quiet)

I cannot understand how the rest of the clue works.

(Other definitions for hush that I've seen before include "(Call for) quiet" , "Soothe" , "Make or become silent or quiet" , "Noiselessness" , "Call for silence" .)

I've seen this clue in the Sydney Morning Herald.

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