The most common and most likely answer to this crossword clue is the 9 letter word FOREIGNER
I've seen this crossword clue in The Daily Telegraph
F
O
R
E
I
G
N
E
R
More clues leading to the result FOREIGNER
- King follows period in office beset by enemy alien
- Stranger supporting unknown number held in mountain
- Not a Brit’s sort of job?
- Alien
- Non-national enemy seizes power with queen
- Alien enemy Queen holding power
- Stranger sort of job on the side
- Not a native name to use in promoting Swiss mountain
- In favour of accepting rule — English, German or Italian, for instance
- One pretending to steal gold for outsider
Buddy explains!

The straight part
We know that "Stranger" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stranger = foreigner.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 FOREIGNER mean?
FOREIGNER noun- A person from a foreign country.
- A private job run by an employee at a trade factory rather than going through the business.