The most common and most likely answer to this crossword clue is the 9 letter word BANQUETTE
I've seen this crossword clue in Financial Times
B
A
N
Q
U
E
T
T
E
Buddy explains!
The straight part
We know that "Seated here at dinner" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case seated here at dinner = banquette.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.
What does BANQUETTE mean?
BANQUETTE noun- A narrow area behind a defensive wall's parapet elevated above its terreplein and used by defenders to shoot at attackers.
- A bench built into a wall, especially one built into a wall of a defensive trench, used for sitting and for shooting at attackers.
- An upholstered bench, e.g., along a wall of a restaurant or lounge area.
- A bench or similar seat on top of a diligence or other public vehicle.
- A sidewalk.