End of game in chaos (5)

I believe the answer is:

omega

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'end' is the definition.
(last letter of the Greek alphabet)

I can't explain the rest of the clue.

(Other definitions for omega that I've seen before include "Last (Gk. letter)" , "Greek finalist" , "Greek long 'o'" , "Ultimate letter" , "letter to Greeks" .)

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

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