also: せいこうのカギ
expression, noun
key to success; key success factor
A set phrase meaning the crucial element or factor that leads to success.
努力こそが成功の鍵だ。
Effort is the key to success.
このプロジェクトの成功の鍵はチームワークです。
The key to this project's success is teamwork.
Literally 'key'; 成功の鍵 is a figurative extension.
Compound of 成功 (success) + の (possessive particle) + 鍵 (key). A straightforward metaphorical phrase.