Disclosure giving priest great joy (10)
I believe the answer is:
revelation
'disclosure' is the definition.
(I know that disclosure can be written as revelation)
'giving priest great joy' is the wordplay.
'giving' says to put letters next to each other.
'priest' becomes 'rev' (short for reverend).
'great joy' becomes 'elation' (I've seen this before).
'rev' next to 'elation' is 'REVELATION'.
(Other definitions for revelation that I've seen before include "enlightening experience" , "Suprising disclosure" , "NT book" , "Surprising disclosure" , "unexpected display" .)