Crossword Genius

Good time for resonance (4)

Ross

I believe the answer is:

boom

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'good time' is the definition.
(I've seen this in another clue)

I cannot understand how the remainder of the clue works.

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(Other definitions for boom that I've seen before include "The noise of increased business activity?" , "Pick up big" , "Deep sound; spar" , "When business is great, opposite to bust" , "Time of great prosperity - hear the sound" .)

I've seen this clue in The Mirror.
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