Crossword puzzle clue "time keepers"

CLOCK, to time with a stopwatch

ED, (short for) education

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

ABBOT, the superior in a monastery

ARK, to put into an ark (a coffer)

BAR, to obstruct or prevent

CAGE, to cage