To outdo someone in their specialty or take away their distinctive role; to steal someone's thunder.
新入社員が短期間で成績を上げ、先輩のお株を奪った。
The new employee improved quickly and stole the senior's thunder.
彼女は料理の腕を上げて師匠のお株を奪ったと言われた。
She improved her cooking skills and was said to have outdone her master.
あのアイデアで先輩のお株を奪うつもりはないよ。
I don't intend to steal the senior's thunder with that idea.