Born in Belfast, Kathy attended Methodist College and then studied French and Russian at Queens University Belfast. The degree course entailed a period in France and a year in Voronezh, Russia. While at University, she was very active in the drama society, playing leading roles in A Midsummer Night's Dream, Private Lives and Buried Child, among many others, and directed L'Alouette (The Lark) by Jean Anouilh.
Clugston worked as a continuity announcer at BBC Northern Ireland from 1996 to 2003, announcing for BBC One Northern Ireland, BBC Two Northern Ireland, and appearing as one of three in-vision announcers on BBC Choice Northern Ireland between 1999 and 2001. She also lent her voice to the BBC Northern Ireland animated comedy series The Folks on the Hill.
Prior to starting at Radio 4, Kathy Clugston spent some years in Amsterdam, working at Radio Netherlands. The Clugston name is believed to be a sept of the clan Stewart.