Game is over on the back of runs, possibly (7)

I believe the answer is:

reversi

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'game' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for reversi that I've seen before include "Game in which captured pieces are inverted" , "Game involving turning over captured pieces" .)

I've seen this clue in The Times and The Sunday Times.

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