Quiet voice that provides cover (7)
I believe the answer is:
shutter
'cover' is the definition.
(I have seen 'Removable cover ' mean 'shutter' so perhaps 'cover' could also mean 'shutter')
'quiet voice' is the wordplay.
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'voice' becomes 'utter' (I've seen this in another clue).
'sh'+'utter'='SHUTTER'
'that provides' acts as a link.
(Other definitions for shutter that I've seen before include "Camera mechanism" , "Moveable window screen" , "It helps provide shade" , "Removable cover" , "Hinged window blind" .)