The most common and most likely answer to this crossword clue is the 5 letter word ARGOT
I've seen this crossword clue in The Guardian
A
R
G
O
T
More clues leading to the result ARGOT
- Special terms in old ship announced
- Particular language to investigate Monet’s work, as it were?
- Specific speech of king in classical garb from the east
- Special language discovered by thieves originally
- Content of jargon primarily this?
- Group talk, activity dissecting pictures etc
- Slang for unmarried girl
- Progress in skill with jargon
- Artist’s upset having understood the vernacular
- Specialised language upcoming artist understood
Buddy explains!

The straight part
We know that "Language" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case language = argot.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 ARGOT mean?
ARGOT noun- A secret language or conventional slang peculiar to thieves, tramps and vagabonds.
- The specialized informal vocabulary and terminology used between people with special skill in a field, such as between doctors, mathematicians or hackers.