The most common and most likely answer to this crossword clue is the 8 letter word TEAHOUSE
I've seen this crossword clue in Financial Times
T
E
A
H
O
U
S
E
More clues leading to the result TEAHOUSE
Buddy explains!

The straight part
We know that "restaurant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case restaurant = teahouse.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 TEAHOUSE mean?
TEAHOUSE noun- A cafe or restaurant that serves tea, usually with light food.
- A public lavatory, particularly as a meeting place for gay men.