n. a person in a secondary role; the second best. (Frequently with play.) I won’t stay around here playing second fiddle for someone half my age and ability!
Play a less important role. In an orchestra or string quartet, music produced by the second violin(s) tends to play more of a supportive harmonic role than the more melodically prominent first violin player(s) play. By extension, “second fiddle” is a companion whose role is less recognized than the person who gets the credit.