The most common and most likely answer to this crossword clue is the 7 letter word LAMBDAS
L
A
M
B
D
A
S
More clues leading to the result LAMBDAS
Buddy explains!

The straight part
We know that "foreign characters" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case foreign characters = lambdas.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 LAMBDAS mean?
LAMBDAS noun- The eleventh letter of the Classical and Modern Greek alphabet, the twelfth of the Old Greek alphabet.
- Unit representation of wavelength.
- The cosmological constant.
- A lambda expression.
- The junction of the lambdoid and sagittal sutures of the cranium
- A lambda baryon
- The percentage change in an option value divided by the percentage change in the underlying asset's price.