Bringing down to earth about what might be not true in prognostication (7-7)

I believe the answer is:

fortune-telling

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'prognostication' is the definition.
(I know that fortune-telling is a type of prognostication)

I don't understand the remainder of the clue.

(Another definition for fortune-telling that I've seen is " What the crystal ball presages".)

I've seen this clue in The Times.

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