The most common and most likely answer to this crossword clue is the 10 letter word ASTRONAUTS
I've seen this crossword clue in Independent
A
S
T
R
O
N
A
U
T
S
More clues leading to the result ASTRONAUTS
Buddy explains!
The straight part
We know that "They may be travelling to a sun/star" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case they may be travelling to a sun/star = astronauts.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 ASTRONAUTS mean?
ASTRONAUTS noun- A member of the crew of a spaceship or other spacecraft that travels beyond Earth's atmosphere, or someone trained to serve that purpose.
- A returnee who frequently flies back and forth between Hong Kong and his/her adopted home country.