Honour a bill on demand (7)
I believe the answer is:
acclaim
'honour' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe there's a link between them I don't understand?
'a bill on demand' is the wordplay.
'a bill' becomes 'ac' (short for account).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'demand' becomes 'claim' (claim is a kind of demand).
'ac'+'claim'='ACCLAIM'
Can you help me to learn more?
(Other definitions for acclaim that I've seen before include "Enthusiastic approval" , "Great public praise" , "Cheer" , "Declare" , "Plaudits" .)