The most common and most likely answer to this crossword clue is the 8 letter word RE-ENTRY
I've seen this crossword clue in Independent
R
E
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E
N
T
R
Y
Buddy explains!
The straight part
We know that "a return to this planet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a return to this planet = re-entry.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 RE-ENTRY mean?
RE-ENTRY noun- The act of entering again.
- The return of a spacecraft into the Earth's atmosphere.
- The reestablishment of possession under a right or rights reserved in a previous conveyance.
- The act of retaking possession of land, etc.; the entry by a lessor upon the premises leased, on failure of the tenant to pay rent or perform the covenants in the lease.
- (of a ukulele) A break in the pitch order of strings.
- The reactivation of (a region of) myocardial tissue by a single, returning impulse.
- The act of retaking the lead by winning a trick.
- A re-entry card.