Grandly taking over diocese at end of this month (2,5)
I believe the answer is:
in style
'grandly' is the definition.
'over diocese at end of this month' is the wordplay.
'over' shows that the letters should be reversed in order.
'diocese' becomes 'ely' (I've seen this before).
'at end of' says to put letters next to each other.
'this month' becomes 'inst' (I've seen this before).
'ely' backwards is 'yle'.
'yle' after 'inst' is 'IN STYLE'.
'taking' acts as a link.
(Other definitions for in style that I've seen before include "(Done) with a grand manner" , "with panache" , "emphatically" , "A la mode" .)