Meaning:
“首” means “first,” and “切,” which literally means “to cut,” is used here in its Japanese kanji sense of “being sold out.” This term, often used by fans of idols, means “first sold out,” referring to shows or albums from their idols, or products endorsed by their idols.
Example:
A: 时代少年团的成员当中谁最受欢迎？
Shídài shàonián tuán de chéngyuán dāngzhōng shuí zuì shòuhuānyíng？
Who of the Typhoon Teens boy band is the most popular?
B: 是刘耀文。因为之前他们发专辑的时候，以他的照片为封面的首切。
Shì liúyàowén。Yīnwèi zhīqián tāmen fā zhuānjí de shíhòu，yǐ tā de zhàopiàn wéi fēngmiàn de shǒuqiē。
It’s Liu Yaowen. When the band released their first album, the one featuring his photo on the cover sold the fastest.