The most common and most likely answer to this crossword clue is the 6 letter word DEADEN
I've seen this crossword clue in Financial Times
D
E
A
D
E
N
More clues leading to the result DEADEN
Buddy explains!

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 DEADEN mean?
DEADEN verb- To render less lively; to diminish; to muffle.
- To become less lively; to diminish (by itself).
- To make soundproof.