Fool here essentially gets to speak in a barely audible voice (6)
I believe the answer is:
mutter
'a barely audible voice' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe there's a link between them I don't understand?
'fool here essentially gets to speak' is the wordplay.
'fool here essentially' becomes 'm' (I can't explain this - if you can you should give a lot more credence to this answer).
'gets' is a charade indicator (letters next to each other).
'to speak' becomes 'utter' (synonyms).
'm'+'utter'='MUTTER'
'in' is the link.
Can you help me to learn more?
(Other definitions for mutter that I've seen before include "carp, > grouse and > beef" , "Talk under one's breath" , "Lack of energy" , "Speak indistinctly or grumble" , "Talk indistinctly in a low voice - a German mother" .)