Important vessel in Havana or Tampa (5)
I believe the answer is:
aorta
'important vessel' is the definition.
(I've seen this in another clue)
'in havana or tampa' is the wordplay.
'in' indicates a hidden word.
'AORTA' is hidden within 'havana or tampa'.
(Other definitions for aorta that I've seen before include "Vital blood vessel" , "Trunk artery from the heart" , "blood flows from it" , "Main artery of body" , "Main human artery" .)