Welcome monarch and roguish chief priest (8)
I believe the answer is:
hierarch
'chief priest' is the definition.
(I've seen this before)
'welcome monarch and roguish' is the wordplay.
'welcome' becomes 'hi' (I've seen this in other clues).
'monarch' becomes 'er' (abbreviation for Elizabeth Regina).
'and' says to put letters next to each other.
'roguish' becomes 'arch' (I've seen this before).
'hi'+'er'+'arch'='HIERARCH'
(Other definitions for hierarch that I've seen before include "Prelate" , "high priest" , "Her chair (anag.)" , "Chief priest" .)