Empty rhetoric, that's a blow (4)

I believe the answer is:

wind

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'a blow' is the definition.
(thesaurus)

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

(Other definitions for wind that I've seen before include "Curl sinuously" , "Move on a twisting path" , "Twist; air movement" , "See 23" , "Not follow straight path" .)

I've seen this clue in The Telegraph.

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