One's utmost to equalise with the champion (5,4)

I believe the answer is:

level best

I'm a little stuck... Click here to teach me more about this clue!

'one's utmost' is the definition.
'level best' can be an answer for 'utmost' (synonyms). I am not certain of the 'one's' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for level best that I've seen before include "Hardest" , "Maximum efforts" , "joint winners?" , "Utmost effort" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.