The most common and most likely answer to this crossword clue is the 9 letter word REFECTORY
I've seen this crossword clue in The Daily Telegraph
R
E
F
E
C
T
O
R
Y
Buddy explains!

The straight part
We know that "dining area" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dining area = refectory.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 REFECTORY mean?
REFECTORY noun- A dining-hall, especially in an institution such as a college or monastery.