Swift attack seizing power (5)

I believe the answer is:

rapid

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'swift' is the definition.
(I've seen this in another clue)

I can't explain the remainder of the clue.

(Other definitions for rapid that I've seen before include "Speedy (5)" , "Quick or swift" , "Express" , "Quickly accomplished" , "Showing pace" .)

I've seen this clue in The Telegraph, The Times and The Independent.

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