Crossword Genius

To win only subsequently leads to optimism seen in an individual (2,3,4)

Ross

I believe the answer is:

on the nose

'to win only' is the definition.
(term when betting on horseracing)

I don't understand the rest of the clue.

(Other definitions for on the nose that I've seen before include "characteristic of glasses?" , "where glasses are found?" , "To win one" , "Exactly in America" , "where glasses rest" .)

I've seen this clue in The Independent.
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