Being intended for the army, a profession also adopted by his brothers, St. John Augustus Clerke, who died a lieutenant-general and colonel 75th Foot, 17 January 1870 and William Clerke, afterwards a major in the 77th Foot, he was sent to the Royal Military College, Great Marlow, where he distinguished himself by his abilities.
He was appointed to an ensigncy without purchase in 1808 and as a subaltern in 28th and 5th Foot, he served through the Peninsular campaigns until the loss of his right leg in the combat at Redinha in 1811 incapacitated him for further active service.
He became the editor of Colburn's United Service Magazine when that journal was started in January 1829, and so continued until July 1842.
On the death of Colonel Gurwood, he was entrusted with the task of seeing the last volume of Selections from the Wellington Despatches through the press.
He possessed a familiar acquaintance with the French, Italian, and Spanish languages, and, although his name does not appear as the author of any scientific or other works, was a very active member of the British Association and of various learned societies.