The most common and most likely answer to this crossword clue is the 10 letter word ASTROLABES
I've seen this crossword clue in Independent
A
S
T
R
O
L
A
B
E
S
Buddy explains!

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 ASTROLABES mean?
ASTROLABES noun- An astronomical and navigational instrument for gauging the altitude of the Sun and stars.