He was a Liberal member of the Legislative Assembly of Ontario from 1987 to 2003 who represented the ridings of Cornwall and Stormont—Dundas—Charlottenburgh.
The Liberals were defeated by the Ontario New Democratic Party in the 1990 election, although Cleary managed to retain his own riding by an increased margin.
He also supported calls for a public inquiry into reports of an organized pedophile ring in the Cornwall area.
Although not a skilled public speaker or a leading figure in the Liberal Party, Cleary was generally regarded as a good community representative during his time in the legislature.
He was not considered to be an especially partisan figure, and in fact criticized party leader Dalton McGuinty for his personal attacks on Mike Harris in 1999.