Judge the writer’s ungrammatical sneer (4)
I believe the answer is:
jibe
'sneer' 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?
'judge the writer's ungrammatical' is the wordplay.
'judge' becomes 'j'.
'the writer' becomes 'i' (the person who is writing these clues).
'ungrammatical' becomes 'be' (I can't explain this - if you can you should believe this answer much more).
'j'+'i'+'be'='JIBE'
(Other definitions for jibe that I've seen before include "provocation" , "Barb" , "Taunt" , "Scoff" , "Mocking remark" .)