Clarke is a professor of preventive medicine and communication at the University of Southern California. His most recent book, written with Susan Evans, is Surviving Modern Medicine (Rutgers University Press, 1998).

With Evans, Clarke co-directs From the Wholesaler to the Hungry, which has received awards from the U.S. Secretary of Agriculture and the UPS Foundation. The project has helped launch almost 150 programs that direct surplus produce to low-income Americans.

Clarke has chaired or served as dean at the University of Washington, the University of Michigan and USC.