Heat a large saucepan over medium-high heat; add ground duck. Cook and stir until no longer pink, 5 to 7 minutes. Drain and discard fat.
Stir chicken broth, crushed tomatoes, spaghetti, heavy cream, and red pepper flakes into the duck. Reduce heat to medium. Cook, stirring frequently, until pasta is tender and sauce is thick and creamy, 15 to 20 minutes.