(A) or a leading article. A newspaper article in large type, by the editor or one of the editorial staff. So called because it takes the lead or chief place in the summary of current topics, or because it is meant to lead public opinion.
The first fiddle of an orchestra and the first cornet-a-piston of a military band is called the leader.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Leader from Fact Monster: