Clingan left Linfield at the end of the 2016–17 season, and on 8 August 2017 it was announced that he had signed for Glenavon. His first goal for the club came in a 6–1 win over Ballymena United. Clingan's expertise from set pieces and penalties proved invaluable, scoring 12 goals as Glenavon ended the 2017–18 season with European qualification.
Clingan left Linfield, joined Glenavon, scored his first goal for them, and contributed to their European qualification.