serve as, hold (a position)
他在两天的庭审期间担任大卫的护卫。
He served as David’s bodyguard during the two-day trial.
基思已经不再担任我的正式护卫和保镖，所以现在他可以开口说话了。
Keith is no longer my official guard and bodyguard, so now he can speak up.