A street in Ottawa, the location of the official residence of the prime minister of Canada.
(Canada, idiomatic) The Canadian prime minister or the government.
By ellipsis from 24 Sussex Drive (“street address of the prime minister's residence”), formerly 24 Sussex Street < 24 + Sussex + street (see also drive). The road was named after Prince Augustus Frederick, Duke of Sussex (1773–1843).
English Wiktionary. Available under CC-BY-SA license.