The most common and most likely answer to this crossword clue is the 6 letter word MURMUR
I've seen this crossword clue in The Guardian
M
U
R
M
U
R
More clues leading to the result MURMUR
- Odd spirit raised for quiet talk
- Whisper from Parisian walls
- . Strange spirit summoned up unnatural sound from organ
- Speak softly when recalling spirit double
- Sound of discontent, as odds reversed?
- Complaint odds have been switched
- Grumble when drinks are sent back
- Rumour of spirit being rejected twice
- Subdued complaint as alcoholic double upended
- Double short knocked back creates complaint
Buddy explains!

The straight part
We know that "W/hisper" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case w/hisper = murmur.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 MURMUR mean?
MURMUR noun- Any low, indistinct sound, like that of running water.
- Soft indistinct speech.
- The sound made by any condition which produces noisy, or turbulent, flow of blood through the heart.
- A muttered complaint or protest; the expression of dissatisfaction in a low muttering voice; any expression of complaint or discontent
- To grumble; to complain in a low, muttering voice, or express discontent at or against someone or something.
- To speak or make low, indistinguishable noise; to mumble, mutter.
- To say (something) indistinctly, to mutter.