Letter from religious figure entering English mansion (7)
I believe the answer is:
epistle
'letter' is the definition.
(I know that epistle is a type of letter)
'religious figure entering english mansion' is the wordplay.
'religious figure' becomes 'st' (abbreviation for saint).
'entering' indicates putting letters inside.
'english' becomes 'E' (abbreviation).
'mansion' becomes 'pile' (pile can mean a large building).
'e'+'pile'='epile'
'st' put inside 'epile' is 'EPISTLE'.
'from' is the link.
(Other definitions for epistle that I've seen before include "Apostle's letter" , "Writing" , "screed" , "may be written off" , "Romans perhaps" .)