There's nothing to blemish his name (5)
I believe the answer is:
oscar
'his name' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe there's an association between them I don't understand?
'there's nothing to blemish' is the wordplay.
'there's nothing' becomes 'o' (I've seen this in other clues).
'to blemish' becomes 'scar' (scarring is a kind of blemishing).
'o'+'scar'='OSCAR'
Can you help me to learn more?
(Other definitions for oscar that I've seen before include "Film prize" , "Man" , "Film-prize statuette" , "Film statuette" , "One of several given to Chicago" .)