Crossword Genius

They roared with wind by two but were swinging by three! (8)

Ross

I believe the answer is:

twenties

'they roared' is the definition.
(the 1920s were the 'roaring twenties')

I can't explain the remainder of the clue.

(Other definitions for twenties that I've seen before include "First adult years" , "Scores" , "decade of frivolity" , "ten years" , "what lies ahead for 27 [TEENAGER]?" .)

I've seen this clue in The Guardian.
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