Son  of Archbishop Henry Lowther Clarke of Bishopscourt, Melbourne.  At the outbreak of the war he had a medical practice  in Peterborough, SA and was married to Constance Anderson, daughter of Bishop and Mrs. Anderson of Riverina.  He enlisted on 16 August 1916 and left on SS Karoola on 19 August 1916.  He served at Suez, Port Said, Moascar and Cairo. 

He was discharged from service for ill-health and returned to Australia on 29 August 1919 on SS Burma.  The Adelaide Chronicle of 10/2/1923 wrote of him that 'after being stationed in Egypt for some time, he accompanied General Allenby's cavalry during their victorious advance though Palestine'.His appointment to the AIF was terminated on 8 November 1919. 

Cyril Clarke returned to his medical practice in Peterborough, South Australia, and also served there as mayor. He died, along with a passenger, on 16 September 1922 in a car accident after the collapse of the right hand rear wheel of his car.