an agent or clergyman in a church of Christianity, such as one who runs a chapel or mission or one who is acting as a deputy for a different minister such as a bishop;
e.g. He intends to become the town vicar and enter the religious life one day.
(noun)
broadly, someone who is acting as an agent of or substitute for someone else, specifically in an administrative position;
e.g. She was named to be the vicar for the duration of his absence.