Vessel's battery discharging poorly (6)
I believe the answer is:
artery
'vessel's' is the definition.
(artery is a kind of vessel)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for artery that I've seen before include "main course" , "Something that could be clogged" , "Felt amazement" , "Vessel taking blood from heart" , "Principle channel of circulatory system" .)