Morsel for the horse's mouth (3)
I believe the answer is:
bit
This clue could be a double definition.
'morsel' is the first definition.
(synonyms)
'horse's mouth' is the second 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?
'for the' acts as a link.
Can you help me to learn more?
(Other definitions for bit that I've seen before include "Small fragment" , "Binary digit; small piece" , "Mouthpiece of brindle or tip of drilling tool" , "Between horse's teeth, this loses control" , "Data measurement unit" .)