Grow furious in diocese with religious education beginning to decline (3,3)
I believe the answer is:
see red
'grow furious' is the definition.
(I've seen this before)
'diocese with religious education beginning to decline' is the wordplay.
'diocese' becomes 'see' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'religious education' becomes 're'.
'beginning to' says to take the initial letters.
The first letter of 'decline' is 'd'.
'see'+'re'+'d'='SEE RED'
'in' acts as a link.
(Other definitions for see red that I've seen before include "Become suddenly angry" , "Burst a blood vessel" , "Be suddenly angry, as bull might" , "Be suddenly angry - like bull?" , "Become angry as bull might" .)