Line from the heart (5)
I believe the answer is:
aorta
'line from the heart' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for aorta that I've seen before include "Main arterial vessel, carrying blood to the heart" , "Body's main artery" , "it's drawing blood!" , "Bloody channel" , "Large trunk artery" .)