The most common and most likely answer to this crossword clue is the 6 letter word PHONIC
I've seen this crossword clue in The Guardian
P
H
O
N
I
C
More clues leading to the result PHONIC
Buddy explains!

The straight part
We know that "Sounding" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sounding = phonic.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 PHONIC mean?
PHONIC adjective- Of or pertaining to sound; of the nature of sound; acoustic.