The most common and most likely answer to this crossword clue is the 6 letter word NANTES
I've seen this crossword clue in The Times
N
A
N
T
E
S
More clues leading to the result NANTES
- Poles with stake in French city
- French port's name engraved in seat
- On return, prepared bread and port
- Back of garden behind houses in French city
- French city where granny put up?
- Port placed by bread for knocking back
- Grandma set to retire somewhere in NW France
- Partners with stake in French city
- Put grandmère back where she might belong
- Grandma has place set up in French city
Buddy explains!

The straight part
We know that "Port" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case port = nantes.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.