Boast new tooth replacement (5)
I believe the answer is:
crown
'boast new tooth replacement' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe there's an association between them I don't understand?
'boast new' is the wordplay.
'boast' becomes 'crow' (to crow about something is to boast about it).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'crow'+'n'='CROWN'
Can you help me to learn more?
(Other definitions for crown that I've seen before include "repair for damaged tooth" , "Headdress, coin" , "Highest part; coin" , "Coin; royal headgear" , "Monarch's headgear" .)