Huckleberry of Fiction refers to the character Huckleberry Finn, a young boy from Mark Twain's novel 'Adventures of Huckleberry Finn'. He is a companion to the runaway slave Jim and together they embark on a journey down the Mississippi River. Huckleberry Finn is a beloved character in American literature, and his adventures have been adapted into films, plays, and other works of art. The four-letter answer to this crossword clue is FINN.