Large blood vessel found in zebra or tapir (5)
I believe the answer is:
aorta
'large blood vessel' is the definition.
'in zebra or tapir' is the wordplay.
'in' indicates the answer is hidden within the clue.
'AORTA' can be found hidden inside 'zebra or tapir'.
'found' is the link.
(Other definitions for aorta that I've seen before include "Bloody channel" , "Trunk artery from the heart" , "A rota (anag)" , "Large blood-vessel" , "Large trunk artery" .)