The most common and most likely answer to this crossword clue is the 10 letter word EARTHWARDS
I've seen this crossword clue in Financial Times
E
A
R
T
H
W
A
R
D
S
Buddy explains!
The straight part
We know that "astronaut goes home" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case astronaut goes home = earthwards.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 EARTHWARDS mean?
EARTHWARDS adjective- Towards the earth; earthward.
- Towards the earth; earthward.