big cheese

 Longman Dictionary of Contemporary English 5++朗文当代英语 5++LDOCE 5++朗文 5++ˌbig ˈcheese noun [countable] informal  IMPORTANTan important and powerful person in an organization – used humorously 要人，大人物〔幽默用法〕

Examples from the Corpus

big cheese• Evidently he was considered a big cheese here, and was greeted by everyone.• One of the big cheeses from NASA gave a speech.Origin big cheese (1900-2000) cheese probably from Urdu chiz “thing”, from Persian

ˌbig ˈcheese nounChineseSyllable  

and Corpus in an an important organization powerful person

big cheese
ˌbig ˈcheese noun [countable] informalan important and powerful person in an organization – used humorously