popular person, in-demand person
その歌手は売れっ子になるだろう。
That singer is likely to become very popular.
ホットな売れっ子はロキシーあたしはどうすれば？
Roxy’s the hot new star—what am I supposed to do?
— シカゴ (2002)
売れっ子の彼女に手が届くと思っているの？
Do you really think you have a chance with a star like her?
— さらば、わが愛／覇王別姫 (1993)
ギャラでこのキッチンを売れっ子なのね
You must be pretty popular if you can afford this kitchen with your fee.
— JUNO／ジュノ (2007)