What the journalist said to have an effect? (7)

I believe the answer is:

impress

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'have an effect?' is the definition.

I cannot understand how the rest of the clue works.

(Other definitions for impress that I've seen before include "Have profound effect upon" , "make good effect" , "Slay" , "Produce a strong, lasting impression on" , "produce a profound effect" .)

I've seen this clue in The Telegraph.

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