play second fiddle to take a subordinate role to someone or something.

☞ The expression derives from the respective roles of the fiddles or violins in an orchestra. Both play first fiddle and play third fiddle are much less common. The implication of playing second fiddle is often that it is somewhat demeaning.

1998Times In A Yank at Oxford she played second fiddle to Vivien Leigh, which never got anyone very far.