Cliff spent nine years of his career with the world's leading nickel producer, Inco Ltd. In his first tenure with Inco, he spent six years in Thompson, Manitoba.

While in Thompson, he worked as Mine Development Engineer and later as Chief Mine Planning Engineer of the Manitoba division of Inco. At the time, Inco was the largest nickel company in the world controlling approximately two-thirds of the free world's nickel supply. Over his six-year period in Thompson, he directed the design and installation of all the equipment for eight mineshafts, a three mile long production tunnel, and examined the feasibility of developing many prospective nickel deposits in the Inco, Thompson inventory.

In 1966, Cliff obtained the role of Assistant General Manager, also acting as the Executive Assistant to the Chief Operating Officer, at Denison Mines – a role he could not refuse.