The most common and most likely answer to this crossword clue is the 9 letter word EXOSPHERE
I've seen this crossword clue in The Times
E
X
O
S
P
H
E
R
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More clues leading to the result EXOSPHERE
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The straight part
We know that "space next to it?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case space next to it? = exosphere.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 EXOSPHERE mean?
EXOSPHERE noun- The uppermost layer of a planet's atmosphere
- An extremely thin atmosphere, as on Saturn's moon Dione