Crossword Genius

Letter read out succeeded after repeat, which you can bet on (3-4)

Ross

I believe the answer is:

gee-gees

'which you can bet on' is the definition.
(gee-gee can informally mean a horse)

I don't understand how the remainder of the clue works.

(Other definitions for gee-gees that I've seen before include "Young children's horses?" , "Horses (informal)" .)

I've seen this clue in The Guardian.
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