Plaster frame of artwork in religious establishment (4)
I believe the answer is:
cake
'plaster' is the definition.
(cake can mean to plaster or cover)
'frame of artwork in religious establishment' is the wordplay.
'frame of' suggests removing the centre (use the outside letters which frame the word).
'in' means one lot of letters goes inside another.
'religious establishment' becomes 'ce' (Church of England).
'artwork' with its centre taken out is 'ak'.
'ak' put inside 'ce' is 'CAKE'.
(Other definitions for cake that I've seen before include "Piece of soap" , "Compact mass of something" , "Something from Dundee, Eccles or Madeira?" , "Confectionery" , "Eg, Genoa, Dundee" .)