expression, godan verb (-mu)
have something on someone; catch someone out; get evidence on someone
Idiomatic expression literally meaning 'grab the tail'. Used when you find a weakness, mistake, or secret that gives you leverage over someone.
彼の不正の尻尾を掴んだ。
I got evidence of his wrongdoing.
相手のミス
I caught the other party's mistake and used it to gain an advantage in the negotiations.