Gosh, a half share in a horse! (3)

I believe the answer is:

gee

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'gosh' is the definition.
(I know that gosh can be written as gee)

I can't explain the remainder of the clue.

(Other definitions for gee that I've seen before include "Horse - surprised expression" , "Goodness" , "7th letter" , "Wow!" , "American exclamation" .)

I've seen this clue in the Evening Standard.

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