One periodically instrumental in public communication? (5)
I believe the answer is:
organ
'one periodically instrumental in public communication?' 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?
'public communication?' is the wordplay.
'public' becomes 'org' (I can't explain this - if you can you should give a lot more credence to this answer).
'communication?' becomes 'AN' (AN is an example).
'org'+'an'='ORGAN'
Can you help me to learn more?
(Other definitions for organ that I've seen before include "Wind and keyboard instrument" , "Possibly stomach" , "Publication - musical instrument" , "Heart or lung, say" , "Soft part of the body which has a specific function" .)