Vital approval for four flats, for example (3,9)
I believe the answer is:
key signature
'example' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'vital approval for four flats' is the wordplay.
I cannot quite see how this works, but
'vital' could be 'key' (key can mean important) and 'key' is found within the answer.
The remaining letters 'signature' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'for' is the link.
Can you help me to learn more?
(Other definitions for key signature that I've seen before include "(In written music) an instruction involving sharps and flats" , "musical reference" , "one flat, say" , "Musical stave's collection of sharps or flats" , "Number of sharps or flats on a musical stave" .)