Principal red route from Isla or Talisker (5)
I believe the answer is:
aorta
'principal red route' is the definition.
'aorta' can be an answer for 'route' (I have seen 'Trunk route' mean 'aorta' so perhaps 'route' could also mean 'aorta'). I am not sure about the 'principal red' bit.
'from isla or talisker' is the wordplay.
'from' indicates a hidden word.
'AORTA' is hidden in the letters of 'isla or talisker'.
Can you help me to learn more?
(Other definitions for aorta that I've seen before include "Tube" , "Large artery of the heart" , "main arterial route" , "Vital blood vessel" , "Major blood vessel" .)