expression, godan verb (-mu)
have a hand in; get involved in; participate in
Idiomatic expression implying involvement in a plan, project, or scheme, often with a nuance of being one of several participants or having some influence.
彼はその新プロジェクトに一枚噛んでいるらしい。
He seems to have a hand in that new project.
He was also involved in that incident.