The most common and most likely answer to this crossword clue is the 10 letter word TRILINGUAL
I've seen this crossword clue in The Times
T
R
I
L
I
N
G
U
A
L
More clues leading to the result TRILINGUAL
Buddy explains!
The straight part
We know that "fluent in three languages" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fluent in three languages = trilingual.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 TRILINGUAL mean?
TRILINGUAL noun- A person who speaks three languages.
- Able to read or speak three languages.
- Expressed or written in three languages.