Mr. and Mrs. Robert J. Clark of Williamsville announce the engagement of their daughter, Elizabeth Anne Clark, to John David Barrett, son of Mr. and Mrs. John H. Barrett of East Amherst. Miss Clark is a graduate of Nardin Academy and is attending Canisius College. Her fiance was graduated from Danbury, Conn., High School and served in the Air Force. He is employed by E3 Environmental Services. An autumn wedding is being planned.