to be treated as less important than sb/sth; to have a less important position than sb/sth else
PLAY SECOND FIDDLE (TO SB/STH)
Meaning of PLAY SECOND FIDDLE (TO SB/STH) in English
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005