According to THR, he will be playing General Wade Eiling, also known as The General, "the head of a black ops army team pursuing Plastique (Kelly Frye) in the hopes of using her as a human weapon. Described as a tall and imposing man, with 'a face carved from years of duty,' Eiling is fanatically intent on protecting American interests around the world and may have ties to a central Flash character."
The character will be introduced in the fifth episode of the first season, and I have no doubt that Clancy is going to be awesome in role. He's set to appear next in Duncan Jones' Warcraft. He also provided the voice of Lex Luthor in several DC animated properties and the voice of Parallax in Green Lantern.