On which excursionists are clamorous after a hush? (6)

I believe the answer is:

outing

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'hush?' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for outing that I've seen before include "journey" , "Revealing orientation" , "Expedition" , "Day trip" , "Short pleasure trip" .)

I've seen this clue in the Evening Standard.

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