Benefactor's name in entrance (5)
I believe the answer is:
donor
'benefactor's' is the definition.
(donor is a kind of benefactor)
'name in entrance' is the wordplay.
'name' becomes 'n' (common abbreviation e.g. on forms).
'in' indicates putting letters inside.
'entrance' becomes 'door' (door is a kind of entrance).
'n' put into 'door' is 'DONOR'.
(Other definitions for donor that I've seen before include "One who gives, maybe blood" , "Charitable giver" , "A giver, perhaps of blood" , "Someone providing" , "One who gives, perhaps blood" .)