Artery being part of that road heading west (5)
I believe the answer is:
aorta
'artery' is the definition.
(I know that aorta is a type of artery)
'part of that road heading west' is the wordplay.
'part of' says the answer is hidden in the clue.
'heading west' says the letters should be written in reverse.
'atroa' is hidden within 'that road'.
'atroa' reversed gives 'AORTA'.
'being' acts as a link.
(Other definitions for aorta that I've seen before include "Body's main artery" , "Main artery of body" , "Vital blood vessel" , "Large artery of the heart" , "A rota (anag)" .)