Clemens was ordained in the early 1960s and spent most of his career at a parish in Kingston. He subsequently retired from active parish ministry and moved to Toronto, Ontario.
In October of 2005, amid discussion of the Vatican's controversial new policy on the ordination of gay priests, Clemens appeared on Vision TV's documentary series 360° Vision and discussed his experiences as a gay man in the priesthood. Clemens told 360 that while he has never violated his priestly promise of celibacy, gay identity is a state of being and not a matter defined solely by sexual activity.
In November 2006 Clemens ran for school trustee for the Toronto Catholic District School Board. He did not have the permission of the Bishop of Kingston (the diocese in which he continues to be incardinated) or the Archbishop of Toronto (the diocese in which he lives) as is required by church law. The Archbishop of Toronto Cardinal Aloysius Ambrozic wrote a letter to Catholics which was read at all Sunday masses in Toronto, informing them that Clemens did not have permission to run for public office. Clemens garnered 29% of the vote for school trustee, losing to the incumbent Catherine LeBlanc-Miller.