An incredible victory at Randwick has put Clear Thinking in the frame for The Kosciuszko.

Paul Messara doesn't know where Clear Thinking's ceiling is, but he is looking forward to finding out after the up-and-coming mare lit up Randwick with a breathtaking Highway Handicap win.

Clear Thinking slipped at the start and had to muster quickly to find a position midfield, forcing apprentice Zac Lloyd to Plan B.

He got the four-year-old into a beautiful rhythm but was faced with a traffic jam of horses as the big field swung for home, finally edging into a narrow gap near the 150m as Messara resigned himself to watching his charge run an eye-catching second or third.

But Clear Thinking ($2.10 fav) motored, finishing fast enough to overhaul Tanglewood ($9.50) by a half-neck with Lisztomania ($21) another long neck away third, much to Lloyd's relief.

"Saved by a nice horse," Lloyd said.

"You wouldn't have found a slower run race, but she settled really 'good' despite the slow speed.

"At the hundred metres, I thought we had no chance - I don't know how she won."

Nor did Messara, who said he was only able to judge Clear Thinking off race day performances because she was such a relaxed horse at home.

But having made the successful transition to Highway Handicap (1200m) grade at just her third start, Messara is hoping she has done enough to attract a slot in the $2 million Kosciuszko (1200m) in October.

"She's a filly with a big future. You can't do more than win three from three, so we will find out where the ceiling is probably next preparation," Messara said.

"She's a horse that doesn't do a hell of a lot at home on the tracks. People ask me, 'how good is she' and I really don't know because what you see out here is where she puts in and on the racetrack she is a very relaxed horse.

"We will give her a break now and probably go to the Kosciuszko if that's an option."

Bred to Northern Hemisphere time by the late Queen Elizabeth II, Clear Thinking is by top stallion Dubawi out of Arrowfield-bred Australian Group 1 winner Sweet Idea.

Put up for sale as part of a breeding and stock dispersal following the Queen's death, Clear Thinking was purchased by Arrowfield for their broodmare band, but she spelled so well in Australia she was given her chance on the racetrack.

Her feats to date have convinced connections to put the mare's breeding career on the backburner, at least for now.

Clear Thinking has firmed into an $8 second pick for The Kosciuszko following Saturday's Randwick performance, behind only $4.50 favourite and defending titleholder Front Page.