Subsequently, celebs heartily cracked gag? (7)

I believe the answer is:

silence

I'm a little stuck... Click here to teach me more about this clue!

'gag?' is the definition.
(I know that gag is a kind of silence)

I don't understand the remainder of the clue.

(Other definitions for silence that I've seen before include "Quiescence" , "License (anag)" , "Soundlessness" , "that's golden" , "Quiet" .)

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

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