The phrase "a leading character" is correct and usable in written English.
It can be used to refer to the main or most important character in a story, film, or play.
Example: "In the novel, the author develops a leading character who faces numerous challenges throughout the plot."
Alternatives: "main character" or "protagonist".
A leading character in this regard is John A. Thain.
"Energy in the executive is a leading character in the definition of good government.
Some of the turns and coincidences (a leading character even pops out of a bush) strain the reader's credulity.
After Clinton agreed to appear at several fund-raisers, Obama turned him into a leading character in his stump speech.
Mr. Liu, in particular, often finds himself a leading character in a Daily News editorial feature called "Weasel Watch".
Back and forth the camera goes, a silent walker, a leading character in a movie without a plot.
His deceptions and self-denial, combined with his fame and status as hero/icon, make him a perfect leading character, both deeply flawed and a product of his time and place in our society.
When we consider the Christmas story, Mary comes a very close second to Jesus himself as a the leading character -- and with good reason.
Along with contemporary games like Street Fighter II, Streets of Rage, and Wurm: Journey to the Center of the Earth, Alisia Dragoon featured a female leading character who can defend herself without the help of a male hero.
There is a potentially wonderful tension to be developed here between Okri and a bellicose leading character who seems totally at odds with the author's usual sympathies.
When McDermid introduced a new leading character in her fourth book, the straight Manchester private eye Kate Brannigan, it precipitated predictable complaints that she had sold out.
