In the early 1920s he migrated to Philadelphia and New York working as a sailor and waiter. He wrote, invited by José Villaverde, in ¡Despertad! to send his “Crónicas de Yanquilandia” when he was already well known by the Galician community of Brooklyn, Newark, Yonkers, New Jersey, etc… He also wrote in the weekly of the Galician Regional Confederation (CRG), Solidaridad Obrera, and from time to time in the newspaper of the FAI, Tierra y Libertad. In 1932 he returned to Galicia. He joined the CNT and, in February 1933, held the position of director of Solidaridad Obrera in A Coruña. His aggressive oratory of a markedly anticlerical tone, was very popular in the region of Noia. In mid-1933, the CNT committee summoned him to join the editorial staff of the CNT newspaper in Madrid and there he collaborated with the Pro Prisoners National Committee. He returned to A Coruña after the failure of the Asturian Revolution, helping to reorganize the CRG by participating in the Galician Committee. In 1935 he moved to Lousame, where through his friend and leader of the Sindicato Minero y Profesiones Varias de San Finx, Enrique Fernández, he began working as a laborer in the tungsten mines. Later he taught the children of the miners. Some time later he went to Huelva to help the Sindicato de Industria Pesquera to guide the steps of the organized sailors. There he is employed again as a miner in Riotinto and takes part in the resistance. Huelva falls in early August 1936 and Sendón flees in a fishing boat to Casablanca, in French Morocco, and from there goes to Oran (Algeria). In October of the same year he returned to Madrid to work in the editorial office of the newspaper CNT. Later he goes to Valencia join the Confederación Levantina of the CNT, becomes delegate of the Regional Levantino in the Comité Nacional da CNT, militating with Federica Montseny. He wrote in the newspaper of the Levantine branch of the CNT, Fragua Social, and continued a very close relationship with other Galician refugees in those places, such as the militant of the Sindicato de Transportes Luis Chamorro, or Manuel Pita Armada from Cariño, soul of the collectivization of the canning industry of the Almeria port of Adra. In mid-July 1937, the CNT decided to use his experience in the United States and sent him along with Juan López, Serafín Aliaga and Avelino González Mallada on a propaganda tour throughout the Americas, although little is known about this. Claro Sendón was in an act in Mexico City where Lazaro Cárdenas also participated. In the United States, Avelino González died in a car accident and Claro Sendón died in New York, at the end of November, at the age of 38 due to typhus. The news of his passing, communicated by the National Committee of the CNT, went unnoticed in Galicia.
(Information taken directly from the “Repertorio biobibliográfico do exilio galego”, Consello da Cultura Galega).