Mother inferior to grumble (7)
I believe the answer is:
maunder
'grumble' is the definition.
The answer and definition can be both to do with communicating as well as being verbs in their base form.
Maybe there's a link between them I don't understand?
'mother inferior to' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'inferior to' becomes 'under' (I've seen this in another clue).
'ma'+'under'='MAUNDER'
Can you help me to learn more?
(Other definitions for maunder that I've seen before include "ramble" , "Drivel" .)