The most common and most likely answer to this crossword clue is the 5 letter word CODED
I've seen this crossword clue in Financial Times
C
O
D
E
D
Buddy explains!

The straight part
We know that "language that needs interpretation" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case language that needs interpretation = coded.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 CODED mean?
CODED verb- To write software programs.
- To add codes to a dataset.
- To categorise by assigning identifiers from a schedule, for example CPT coding for medical insurance purposes.
- To encode.
- To encode a protein.
- To call a hospital emergency code.
- Of a patient, to suffer a sudden medical emergency (a code blue) such as cardiac arrest.
- Encoded; written in code or cipher.