Sister lost two sets producing some sonnets (7)
I believe the answer is:
sestets
'some sonnets' is the definition.
The answer and definition can be both related to communication as well as being plural nouns.
Perhaps you can see an association between them that I can't see?
'sister lost two sets' is the wordplay.
'two sets' means two replacements for 'set'.
'sister' becomes 's' (this could be a standard abbreviation which I don't know about).
'lost' indicates an anagram.
'set'+'set'='setset'
'setset' with letters rearranged gives 'estets'.
's'+'estets'='SESTETS'
'producing' acts as a link.
Can you help me to learn more?
(Other definitions for sestets that I've seen before include "Poetry" , "Six performing together" .)