Crone changed energy for extra song (6)
I believe the answer is:
encore
'extra song' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'crone changed energy' is the wordplay.
'changed' is an anagram indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
'crone' with letters rearranged gives 'encor'.
'encor'+'e'='ENCORE'
'for' is the link.
Can you help me to learn more?
(Other definitions for encore that I've seen before include "Sing it again, please" , "We need more" , "Bis!" , "Call for additional performance" , "Request for repeat performance" .)