Talk that, though quiet, does prove disturbing (7)
I believe the answer is:
prattle
'talk that though quiet does prove disturbing' is the definition.
'prattle' can be an answer for 'talk' (prattle is a kind of talk). I'm not sure about the rest of the definition.
'talk that though quiet' is the wordplay.
I cannot really understand how this works, but
'talk' could be 'rattle' (I have seen 'Trivial talk' mean 'rattle' so perhaps 'talk' could also mean 'rattle') and 'rattle' is found in the answer.
'quiet' could be 'p' (music symbol for 'piano', ie soft or quiet) and 'p' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for prattle that I've seen before include "Chat inconsequentially" , "rabbit" , "Be vapidly garrulous" , "Talk inconsequentially" , "Talk emptily" .)