Bookmakers' semaphore (6)

I believe the answer is:

tictac

(Other definitions for tictac that I've seen before include "Bookmakers' signing" , "System of signalling used by bookies" , "Russian water-urn" , "Racecourse bookmakers' signalling system" , "Racecourse semaphore" .)

I've seen this clue in The Mirror.

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