He was born in
Moose Factory to James Stewart Clouston (1826–1874), the last
Chief Factor of the
Hudson's Bay Company (HBC), and his wife Margaret, daughter of Robert Seaborn Miles (1795–1870), in his time also Chief Factor for the HBC and
Sheriff of
Rupert's Land. His grandfather was agent for the HBC at
Stromness on
Orkney, where his family had lived since the end of the 17th century, descended from Richard Clouston (1626–1666), 16th of Clouston and Netherbigging, Stromness. Clouston received his education at the
High School of Montreal and then worked for one year for the Hudson's Bay Company before commencing employment at the Bank of Montreal as a clerk in 1865. He served as vice-president of the Royal Trust Company and as a director of the Guarantee Company of North America, the Canadian Cottons, Limited, the Canada Sugar Refining Company, the Ogilvie Flour Mills Company, and the Kaministikwia Power Company. He was chairman of the Canadian board of the Liverpool & London & Globe Insurance Company and the Mutual Life Insurance Company of New York. ==Family==