Terrible though not loud stream of abuse (6)
I believe the answer is:
earful
'stream of abuse' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'terrible though not loud' is the wordplay.
'terrible' becomes 'fearful' ('fearful' can be a synonym of 'terrible').
'though not' suggests deleting specific letters.
'loud' becomes 'f' (A musical term).
'fearful' with 'f' removed is 'EARFUL'.
Can you help me to learn more?
(Other definitions for earful that I've seen before include "Ale fur (anag.)" , "Ticking-off" , "Informally, a strong reprimand of aural content" , "Reprimand (informal)" , "Load of abuse (received)" .)