You might say Frontier Circus, which Revue sold to CBS in 1961, was Wagon Train goes to the circus.
Both Westerns were anthology series at their core, with a small cast of regulars, and the plots all centering not on those regulars, but on ancillary ones. However, Frontier Circus didn't have the staying power of Wagon Train, and lasted just 1 season.
Chill Wills, who'd been on the Universal payroll as the uncredited voice of "Francis, The Talking Mule" in a series of films with Donald O'Connor, toplined as the co-owner of the traveling circus, with John Derek and Richard Jaeckel as the other regulars. Wills would land another series gig 5 years later in a TV version of The Rounders, having co-starred in the film version a few years earlier. John Derek is better remembered today after then-wife Bo became a big star in the late 70's (i.e. "10" with Dudley Moore).
In the opener, "Depths of Fear", the town drunk (Aldo Ray), a former lion tamer now down on his luck, is given a second chance, and an opportunity to replace the troupe's current lion tamer (James Gregory, fresh from The Lawless Years) who's also an abusive bully.