Wiktionary
big break
n. (context entertainment idiomatic English) A breakthrough, especially the first big hit of a previously unknown performer or performers in the entertainment industry.
Wikipedia
Usage examples of "big break".
What a shame, to have spent years hoping and dreaming for the big break, that shot on prime-time TV& and to miss it due to Thorazine.
This bottomless remark was over the top, and was my first big break.
A real waiter, not a pretty-face biding time till the next big break.
He regarded this as his big break, and crowed vastly to his family in cheerful letters that made fun of the Pope.