The most common and most likely answer to this crossword clue is the 4 plus 4 letter word FREE PORT
I've seen this crossword clue in The Daily Telegraph
F
R
E
E
P
O
R
T
More clues leading to the result FREE PORT
Buddy explains!
The straight part
We know that "There’s no duty here/no charge for wine" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case there’s no duty here/no charge for wine = free port.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.