Every kind of repetition is initial repetition (12)
I believe the answer is:
alliteration
'initial repetition' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'every kind of repetition' is the wordplay.
'every' becomes 'all' (similar in meaning).
'kind of repetition' becomes 'iteration'.
'all'+'iteration'='ALLITERATION'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for alliteration that I've seen before include "Repeated first letters" , "Peter practised poetic ploy perfectly" , "Poetic rhyming device using words with the same initial letter" , "Successive starts sounding similarly" , "verse technique" .)