Here to spy producing tricky words? (3,6)

I believe the answer is:

hey presto

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'tricky words?' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for hey presto that I've seen before include "before your very eyes" , "Conjuror's exclamation at the climax of a trick" , "Magic words" , "tricky words?" , "suddenly, as if by magic" .)

I've seen this clue in The Independent and The Sun.

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