The most common and most likely answer to this crossword clue is the 5 letter word SCHWA
I've seen this crossword clue in The Times
S
C
H
W
A
More clues leading to the result SCHWA
- Small drink's drunk with unobtrusive sound
- Unstressed syllable in school was cut
- Indistinct sound check in South Australian state
- Sound unstressed after chief visiting was abused
- Right-of-centre putsch against Washington — sound of America's extremists?
- Common sound coming from some Bosch washers
- Indistinct sound was cut short after request for silence around clubs
- Helping of kirschwasser? It ends with one
- . School with American vowel sound?
- Stress-free character seemingly calm, having walked away initially
Buddy explains!

The straight part
We know that "Indistinct sound" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case indistinct sound = schwa.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 SCHWA mean?
SCHWA noun- An indeterminate central vowel sound as the "a" in "about", represented as /ə/ in IPA.
- The character ə.