1
general::
Phrase(s): play second fiddle (to someone)
Fig. to be in a subordinate position to someone. • I’m tired of playing second fiddle to John. • I’m better trained than he, and I have more experience. I shouldn’t always play second fiddle.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Assume a subsidiary role to someone, as in Mary resented always playing second fiddle to her older sister. This term alludes to the part of second violin in an orchestra. Although many would argue it is as important as first violin, it is the idea of subordinacy that was transferred in the figurative term, so used since about 1800.
American Heritage Idioms