Clark was born Nora Golding on March 8, 1943 in Sarnia, Ontario, Canada, and raised in Toronto, the daughter of Eleanor Almond (née McNaughton) and George Raymond Golding. She attended Northern Secondary School and, later, at the Royal Academy of Dramatic Arts (in London, UK) and the Stella Adler Studio of Acting. Her younger step-sister is actress
Linda Thorson (both appeared on
Emily of New Moon (1998)).