second banana

/S EH1 K AH0 N D B AH0 N AE0 N AH0/
noun
  1. 1

    A comedian who plays a secondary or supporting role, especially as straight man and traditionally in vaudeville or burlesque theatre.

    โ€œHe grew disenchanted with playing second banana and never getting credit for the laughter.โ€

  2. 2

    A person who serves in a supporting, secondary, or subsidiary capacity; an assistant.

    โ€œThe plumber left his second banana behind, to finish installing my new sink.โ€

Source: https://en.wiktionary.org/wiki/second%20banana