Hearty leaders (8)
I believe the answer is:
arteries
'hearty leaders' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Perhaps you can see an association between them that I don't see?
This is all the clue.
Can you help me to learn more?
(Other definitions for arteries that I've seen before include "Major thoroughfares for important traffic" , "Blood vessels leading from the heart" , "Blood vessels - major roads" , "Vessels that carry blood from the heart to the body" .)