He had failed in the execution of his duty.

他未能履行职责。

《牛津词典》

He was arrested for obstruction of a police officer in the execution of his duty.

他因妨碍警察执行公务而被逮捕。

《牛津词典》

Thus encouraged, he proceeded gravely to the execution of his duty, and, strictly forbidding all aggravating expressions on either side.

经过这番鼓励，他才开始严肃地履行他的职责，严格制止任何一方惹怒对方。

youdao

Milton actually wrote that it was the duty, not just the right but the duty, of a nation to rise up and dethrone through execution an unjust, though legitimate, king.

弥尔顿实际上写道，站起来通过处决而废黜，一个尽管合法却不公正的国王是一个国家的义务,不仅仅是权利，而且还是义务。

耶鲁公开课 - 弥尔顿课程节选

Any manager who determines in his judgment that achievement of the minority brokerage goals is not consistent with his best execution duty may simply refuse to do business with minority brokers.

FORBES: Minority-Owned Brokerages vs. Pension Brokers: Fighting for the Same Commission Dollars (January 1, 2002 )