expression, godan verb (-ru)
make a start; get off to a start
Used for beginning a race, competition, project, or new phase. Often implies a decisive or energetic start.
彼は100メートル走で好スタートを切った。
He got off to a good start in the 100-meter dash.
新年度がスタートを切った。
The new fiscal year has begun.
スタートする is a simple suru-verb meaning 'to start', while スタートを切る is a set phrase that emphasizes the act of making a start, often in a race or a new endeavor.
Combination of the loanword スタート (start) and the verb 切る (cut), literally 'to cut a start', an idiom for beginning something decisively.