Beat time (6)
I believe the answer is:
rhythm
This clue is a double definition.
'beat' is the first definition.
(I know that beat can be written as rhythm)
'time' is the second definition.
(I know that rhythm is a type of musical time)
(Other definitions for rhythm that I've seen before include "Sense of musical beat" , "Musical pulse" , "Regular succession of sounds" , "Strong regular repeated pattern of sound" , "Regular succesion of sounds" .)