Port not vintage — enjoy last of Semillon (3,5)
I believe the answer is:
new haven
'port' is the definition.
(port in Connecticut)
'not vintage enjoy last of semillon' is the wordplay.
'not vintage' becomes 'new'.
'enjoy' becomes 'have' (to enjoy can mean have or have use of).
'last of' suggests the final letters.
The last letter of 'semillon' is 'n'.
'new'+'have'+'n'='NEW HAVEN'
(Other definitions for new haven that I've seen before include "English port" , "E. Sussex port" , "Port in East Sussex" , "Ferry port" , "Location of US university" .)