One periodically instrumental in public communication? (5)
I believe the answer is:
organ
'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 a link between them I don't understand?
'one' is the wordplay.
I cannot really understand how this works, but
'one' could be 'an' (I've seen this in other clues) and 'an' is found in the answer.
This may be the basis of clue (or it may be nonsense).
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" .)