The most common and most likely answer to this crossword clue is the 9 letter word ROOMETTES
I've seen this crossword clue in The Times
R
O
O
M
E
T
T
E
S
Buddy explains!
The straight part
We know that "small confined spaces" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case small confined spaces = roomettes.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 ROOMETTES mean?
ROOMETTES noun- A small private compartment, for one person, in a railroad sleeping car