Priest takes delight in this book of his (10)
I believe the answer is:
revelation
'this book of his' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'priest takes delight' is the wordplay.
'priest' becomes 'rev' (short for reverend).
'takes' means one lot of letters go next to another.
'delight' becomes 'elation' (elation is delight or glee).
'rev'+'elation'='REVELATION'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for revelation that I've seen before include "joy?" , "NT book" , "telling statement" , "enlightening book?" , "Suprising disclosure" .)