or A-game, a-game
a person’s best effort, abilities, or achievement: The candidate brought her A game to the debate.
Origin of A game
in reference to a sports contest, with the letter A indicating peak performance
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020
Examples from the Web for a game
Some have suggested Letterman needed Leno as competition to bring his A-game night after night.Yes, Stephen Colbert Will Be Great as Host of CBS’s ‘Late Night’|Pete Dominick|April 10, 2014|DAILY BEAST
Working with a guy like Željko is like playing basketball with an NBA star—you have to bring your A-game.