Bets on footballers and retires (5)

I believe the answer is:

backs

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

I cannot understand how the remainder of the clue works.

(Other definitions for backs that I've seen before include "Reverses" , "Gives support or one's blessing to" , "Defensive players" , "Levy of money" , "Helps or supports with money" .)

I've seen this clue in The Globe and Mail.

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