Crossword puzzle clue "beat keepers"

METRONOME, a mechanical device which indicates the exact tempo of a piece of music by producing a clicking sound from a pendulum with an adjustable period of swing

PATROLMAN, a police officer on duty on a beat

ABBOT, the superior in a monastery

ARK, to put into an ark (a coffer)

BAR, to obstruct or prevent

CAGE, to cage

CAN, to put in a cylindrical container