She was born at 10 Morton Street, Leith, near Edinburgh, Scotland, on 22 October 1883, the eldest daughter of Thomas Charles McNab, a wire-cloth weaver, and his wife, Mary Deas Fraser. Her father was a high-profile figure in local politics, including being a director of Leith's co-operative association, and played a large part in moulding Clarice's radical and political beliefs in Labour politics.
