McClure is the posthumous son of one of James Abercrombie‘s captains, first cousin of Oscar Wilde and spends his childhood under the care of his godfather, General John Le Mesurier, governor of Alderney, by whom he is educated for the army. The McClures are of Highland Scots ancestry, being a sept of Clan MacLeod of Harris. He enters the navy, however, in 1824, and twelve years later gains his first experience of Arctic exploration as mate of HMS Terror in the expedition (1836–1837) commanded by Captain George Back.
Upon his return he obtains his commission as lieutenant, and from 1838 to 1839 serves on the Canadian lakes, being subsequently attached to the North American and West Indian naval stations, where he remains until 1846. Two years later he joins John Franklin‘s search expedition (1848–1849) under James Clark Ross as first lieutenant of HMS Enterprise.
After he returns from the first Franklin search expedition, a new search expedition is launched in 1850, with Richard Collinson commanding the HMS Enterprise and McClure, as his subordinate, given the command of HMS Investigator. The two ships set out from England, sail south on the Atlantic Ocean, navigate through the Strait of Magellan to the Pacific Ocean with the assistance of steam-sloop HMS Gorgon, where they become separated and have no further contact for the rest of their respective journeys.
The HMS Investigator sails north through the Pacific and enters the Arctic Ocean by way of the Bering Strait, and sails eastward past Point Barrow, Alaska to eventually link up with another British expedition from the northwest. Although the HMS Investigator is abandoned to the pack ice in the spring of 1853, McClure and his crew are rescued by a party from the HMS Resolute, one of the ships under the command of Sir Edward Belcher that are sailing from the east, after a journey over the ice by sledge. Subsequently he completes his journey across the Northwest Passage. HMS Resolute itself does not make it out of the Arctic that year and is abandoned in ice, but later recovered. The wood from that ship becomes quite famous later.
Thus, McClure and his crew are the first both to circumnavigate the Americas, and to transit the Northwest Passage, considerable feats at that time. The HMS Enterprise, meanwhile, having arrived at Point Barrow in 1850 a fortnight later than the HMS Investigator, finds its passage blocked by winter ice and has to turn back and return the following year.
Upon his return to England, in 1854, McClure is court martialed for the loss of the HMS Investigator, which is automatic when a captain loses his ship. Following an honourable acquittal, he is knighted and promoted to post-rank, his commission being dated back four years in recognition of his special services. McClure and his crew share a great monetary reward of £10,000 awarded them by the British Parliament. He subsequently is also awarded gold medals by the English and French geographical societies. In 1855 he is elected a member of the American Antiquarian Society.
From 1856 to 1861 McClure serves in Eastern waters, commanding the division of the Naval Brigade before Canton in 1858, for which he receives a CB in the following year. His latter years are spent in a quiet country life. He attains the rank of rear admiral in 1867, and of vice admiral in 1873. He dies on October 17, 1873 and is buried in Kensal Green Cemetery, London.