Moment of truth — for the crisp eater? (6)

I believe the answer is:

crunch

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'moment of truth' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for crunch that I've seen before include "Moment of truth" , "Crush with the teeth" , "moment of difficulty" , "Chew something hard" , "Process (lots of data)" .)

I've seen this clue in The Times.

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