Frontrunner from UN maybe lacking empathy at first (9)
I believe the answer is:
pacemaker
'frontrunner' is the definition.
(a pacemaker runs at the front)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for pacemaker that I've seen before include "Device inserted into chest to stimulate heart" , "Heart patient's aid" , "Electrical device put in heart to stimulate pulse" , "Device inserted in body to strengthen heartbeat" , "Implanted device to control the heartbeat" .)