Friend describes a nameless Roman Catholic as grand (8)
I believe the answer is:
palatial
'grand' is the definition.
(I've seen this in another clue)
'friend describes a nameless roman catholic' is the wordplay.
'friend' becomes 'pal' (pal can mean a friend).
'describes' is an insertion indicator (describe can mean to form the outline of).
'a nameless roman catholic' becomes 'latia' (I can't explain this - if you can you should believe this answer much more).
'pal' placed around 'latia' is 'PALATIAL'.
'as' is the link.
Can you help me to learn more?
(Other definitions for palatial that I've seen before include "Magnificently appointed" , "Like a house fit for royalty" , "House fit for a king" , "Sumptuous and spacious" , "Of building, spacious and splendid, fit for a king" .)