Vessel found in Zambia or Tanzania (5)
I believe the answer is:
aorta
'vessel' is the definition.
(blood vessel)
'in zambia or tanzania' is the wordplay.
'in' indicates the answer is hidden within the clue.
'AORTA' can be found hidden inside 'zambia or tanzania'.
'found' acts as a link.
(Other definitions for aorta that I've seen before include "Main arterial vessel, carrying blood to the heart" , "Tube" , "claret supplier" , "Major blood vessel" , "Blood carrier" .)