Longtao generally means figurant, because they always wear Longtao robes to serve as a foil to main actors on the stage.

龙套”就是群众演员，于他们各色龙套衣而得名。

During my colleagues, there are so many superexcellent ones, trickish ones, adulatory ones, who are doing better than me, and I have fallen to a walk-on.

同事中，能力卓越者、攻于心计者、溜须拍马者，强于我更是不胜其数，自己现在已沦为一个跑龙套。