noun
chief editor; managing editor
Specifically the top editorial position at a newspaper, magazine, or publishing house.
彼は新聞社の主幹として最終的な記事の責任を負っている。
As the chief editor of the newspaper, he bears the final responsibility for the articles.
noun
Broader use for the head or manager of an organization, department, or project; less common than sense 1.
プロジェクトの主幹として、彼はチーム全体を統括している。
As the manager of the project, he oversees the entire team.
Compound of 主 (しゅ, 'main, chief') and 幹 (かん, 'trunk, core'), literally 'main trunk', metaphorically the central person in an organization.