The most common and most likely answer to this crossword clue is the 9 letter word PLANETARY
I've seen this crossword clue in The Guardian
P
L
A
N
E
T
A
R
Y
More clues leading to the result PLANETARY
Buddy explains!

The straight part
We know that "Earth’s" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case earth’s = planetary.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 PLANETARY mean?
PLANETARY noun- A planetary nebula.
- Of, or relating to planets, or the orbital motion of planets.
- Of, or relating to the Earth; terrestrial.
- Of, or relating to the whole Earth; global.
- (of a gear train) epicyclic