Good man maps out marks of approval (6)
I believe the answer is:
stamps
'marks of approval' is the definition.
The answer and definition can be both related to communication as well as being plural nouns.
Perhaps there's an association between them I don't understand?
'good man maps out' is the wordplay.
'good man' becomes 'st' (abbreviation for saint).
'out' indicates an anagram (out can mean wrong or inaccurate).
'maps' anagrammed gives 'amps'.
'st'+'amps'='STAMPS'
Can you help me to learn more?
(Other definitions for stamps that I've seen before include "Tramples" , "Philatelists study them" , "Puts the foot down on letters" , "Postal tokens" , "Philatelists collect them" .)