Benefactor's name inside entrance (5)
I believe the answer is:
donor
'benefactor's' is the definition.
(donor is a kind of benefactor)
'name inside entrance' is the wordplay.
'name' becomes 'don' (**).
'inside' says to take the centre.
'entrance' becomes 'port'.
The middle of 'port' is 'or'.
'don'+'or'='DONOR'
(Other definitions for donor that I've seen before include "One who gives blood, for instance" , "Charitable giver" , "Maker of gift" , "Organ giver?" , "Philanthropist" .)