The material placed in cathedral, as if from heaven? (10)
I believe the answer is:
ethereally
'as if from heaven?' is the definition.
(ethereal means beautiful in an otherworldly way)
'the material placed in cathedral' is the wordplay.
'material' becomes 'real' (associated in meaning).
'placed in' indicates putting letters inside (I've seen this in other clues).
'cathedral' becomes 'ely' (ely is a cathedral city in cambridgeshire).
'the'+'real'='thereal'
'thereal' put into 'ely' is 'ETHEREALLY'.
(Other definitions for ethereally that I've seen before include "Spiritually" , "airily" , "in heavenly style" .)