Green’s Dictionary of Slang

a horse that seems a certain winner.

1938		D. Runyon ‘All Horse Players Die Broke’ in Runyon on Broadway (1954) 714: This mare Cara Mia is a stick-out.
1956		‘Toney Betts’ Across the Board 74: He makes a fuzzy-wuzzy mark on it around the number of a horse in the fourth race. That’s what he means by a fuzzy, you know, a stickout.