Philanthropist's name inscribed in entrance (5)
I believe the answer is:
donor
'philanthropist's' is the definition.
(I've seen this before)
'name inscribed in entrance' is the wordplay.
'name' becomes 'n' (common abbreviation e.g. on forms).
'inscribed in' is an insertion indicator.
'entrance' becomes 'door' (door is a kind of entrance).
'n' placed into 'door' is 'DONOR'.
(Other definitions for donor that I've seen before include "blessed person, relatively" , "Philanthropist" , "Benefactor, giver" , "Maker of gift" , "One giving to a cause" .)