Heartbeat indicator (5)
I believe the answer is:
pulse
'heartbeat indicator' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pulse that I've seen before include "regular bodily motion!" , "Vegetable (taken by doctors?)" , "Vitality" , "Edible seed from various pod plants" , "runner, possibly" .)