Beating a bean, say (5)
I believe the answer is:
pulse
I believe this clue is a double definition.
'beating' is the first definition.
(I've seen this before)
'a bean say' is the second definition.
(I know that bean is a type of pulse)
(Other definitions for pulse that I've seen before include "Musical rhythm" , "Musical beat; edible seeds" , "Heart rhythm" , "Vibration" , "Rhythmic throb" .)