right-hand man

Từ điển Oxford Advanced Learner 8th

ˌright-hand ˈman [right-hand man right-hand men] BrE NAmE noun singular
a person who helps sb a lot and who they rely on, especially in an important job
•the President's right-hand man

Example Bank:
•Communications chief, Alastair Campbell, became Tony Blair's right-hand man in Downing Street.
•He agreed to the deal after consulting his lawyer and right-hand man, Charles Alton.