Clark Orman was working as a night porter when he enlisted in the AIF on 27 October 1916. Although he was living in Victoria Parade, East Melbourne, he enlisted at Geelong. He was just over 21, 5'7", with light blue eyes and brown hair. His father was his next of kin and lived at 9 L'Avenue, Newtown, NSW. The family had come from Narrabri, NSW, where Clark was born; another three Ormans, all brothers, enlisted from Narrabri, with one being killed in action on the Western Front. It is highly likely that they were cousins of Clark Orman. 

The 7/2 Cyclists were reinforcements. Clark trained with the Corps at Royal Park, Melbourne, before leaving on HMAT  'Medic'  bound for Plymouth on 16 December, 1916, arriving on 13 February, 1917. From Plymouth, he was sent to Etaples, France, joining his unit on 19 May, 1917. He served on the Western Front until 9 February, 1918, where he was gassed and in hospital for two weeks before returning to the Front. Again, on 3 March, he was both wounded and gassed, but must not have been badly injured, as he was sent on leave to England on 9 March. From then on, illnesses seem to have plagued him: scabies in April, 1918; sick in May; an inflammation of the connective tissue in June, the result of a gunshot to his buttock ; tonsillitis in October. In addition, there were several charges of AWL. 

Clark Orman was discharged from military service in Sydney on 7 July, 1920.

In October, 1919, he was married to Dorothy Skinner Sutherland in England. In 1949, they were living at 1 Leofrane Ave., Marrickville, NSW.