Beat a lentil, say (5)
I believe the answer is:
pulse
'beat' is the definition.
(pulsing is a kind of beating)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for pulse that I've seen before include "Bean - throb" , "Vegetable (taken by doctors?)" , "Rhythmic throbbing" , "Sign of life" , "It beats - peas and beans" .)