Prior to his parliamentary career, Joe Clark also operated as a tailor at Coonamble and later at Dover Heights in Sydney. He went on to serve as an alderman Coonamble Council for nine years, including three terms as Mayor of Coonamble. He was president of the Coonamble branch of the Australian Labor Party and was president of the Castlereagh Electorate council. He was closely associated with the N.S.W. State Labor Group under the leadership of Jack Beasley.
Clark sat on a number of industry committees and bodies, including the Australian Meat Industry Commission from 1942 to 1943, the Federal Meat Advisory Committee from 1943 to 1946, and in 1946 he led a delegation to the Iron and Steel Committee. He was Chairman of Committees and Deputy Speaker in the House from 1946 to 1949.