The most common and most likely answer to this crossword clue is the 9 letter word WITHDRAWN
I've seen this crossword clue in Independent
W
I
T
H
D
R
A
W
N
More clues leading to the result WITHDRAWN
- Uncommunicative comedian lured outside hotel
- Reserved, as cash in bank can be
- … and portrayed as shy
- Quiet humour getting hearts tense
- Lottery in hand, oddly, after card removed
- Shy when in the company of Haggard
- Comedian, tired after second of shows, is taken out
- Scratched and pinched
- Retired in the company of lottery winners, essentially
- Removed for being shy
Buddy explains!

The straight part
We know that "Quiet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case quiet = withdrawn.The cryptic/wordplay part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What does WITHDRAWN mean?
WITHDRAWN verb- To pull (something) back, aside, or away.
- To stop talking to, or interacting with, other people and start thinking thoughts that are not related to what is happening around.
- To take back (a comment, etc); retract.
- To remove, to stop providing (one's support, etc); to take out of service.
- To extract (money from an account).
- To retreat.
- To be in withdrawal from an addictive drug etc.
- Removed from circulation
- Introverted; not inclined to interact with other people