Ordinary song (8)
I believe the answer is:
standard
This clue could be a double definition.
'ordinary' is the first definition.
(I've seen this before)
'song' is the second definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
Can you help me to learn more?
(Other definitions for standard that I've seen before include "The usual range" , "Touchstone, benchmark 98)" , "'Reference point, touchstone (8)'" , "Ceremonial flag" , "Flag; criterion" .)