Sign in a bar: "Cola left to get drunk" (4,4)
I believe the answer is:
alto clef
'sign in a bar' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'cola left to get drunk' is the wordplay.
'to get drunk' indicates anagramming the letters.
'cola'+'left'='colaleft'
'colaleft' with letters rearranged gives 'ALTO CLEF'.
Can you help me to learn more?
(Another definition for alto clef that I've seen is " Stave marking".)