He travelled and performed with fellow folk musicians including Pete Seeger, Woody Guthrie and Lead Belly.
Along with his first wife, Adrienne Claiborne, he wrote the song Listen Mr. Bilbo and several others, and hosted a folk radio show for a time.
Robert became an editor at Scientific American, only to lose his job in 1960 after the FBI visited and pointed out to the senior staff that he had been called before the House Un-American Activities Committee hearings as an ex-communist, and had refused to testify.
[1] After losing his job, Claiborne found bread and butter work writing and editing some of the famous Time-Life series of science books.
During this late period, he also produced Saying What You Mean, a practical guide for writers, researched by his daughter, Amanda Claiborne; the less well-received Roots of English, which included a 're-assembled' hypothetical Indo-European dictionary; and Loose Cannons and Red Herrings: a book of lost metaphors, about metaphors that have merged into common usage to the point that the source of their meaning is obscured.