The most common and most likely answer to this crossword clue is the 9 letter word INAUDIBLE
I
N
A
U
D
I
B
L
E
More clues leading to the result INAUDIBLE
- At home, a horribly bullied student’s withdrawn and silent
- Even the most generous would be deaf to such appeals
- Non-U sportsman following in car is unlikely to be caught
- Car held by popular belief, oddly, to be
- Popular car practically ran without noise
- Car manufacturer, British, invested in new line that’s silent
- Not picked up in foreign car, be left inside
- Impossible to catch popular German car — tooted endlessly
- Non-U Tory following in car unlikely to be caught?
Buddy explains!

The straight part
We know that "silent" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case silent = inaudible.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 INAUDIBLE mean?
INAUDIBLE adjective- Unable to be heard or not loud enough to be heard.