Such music may be a piece of indefinite length (6)
I believe the answer is:
string
'such music' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'a piece of indefinite length' is the wordplay.
I cannot quite see how this works, but
'piece' could be 'ring' (I have seen 'Piece of jewellery ' mean 'ring' so perhaps 'piece' could also mean 'ring') and 'ring' is located in the answer.
The remaining letters 'st' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'may be' is the link.
Can you help me to learn more?
(Other definitions for string that I've seen before include "Part of racket" , "Piece of catgut stretched on violin" , "A - - of Pearls" , "Something for tying up" , "Cord for a group of racehorses" .)