Musical work, usually not American (4)
I believe the answer is:
opus
This might be a double definition.
'musical work' is the first definition.
(I've seen this before)
'usually not american' is the second definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
Can you help me to learn more?
(Other definitions for opus that I've seen before include "Composer's catalogue number" , "Major work" , "(Numbered) musical composition" , "Composition - magnum __" , "Musical piece" .)