The most common and most likely answer to this crossword clue is the 9 letter word EARTHLING
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result EARTHLING
- Strangely thin, large human
- Person’s attention given to obsession about Lima
- Person doing wiring interrupted by learner
- No one from space is real thing, unfortunately
- Listener with obsession about large sci-fi character
- Right lane to turn one of us to strangers
- Person left inside doing electrical work
- Land fish, one that’s out of this world?
- . One of us needing another large hint
- Strange alien, right? Not I!
Buddy explains!

The straight part
We know that "Strange alien, right? Not I!" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case strange alien, right? not i! = earthling.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 EARTHLING mean?
EARTHLING noun- A sentient being who's a member of a species native to Earth.
- A lesbian woman.