Start of a website manager's email address, maybe (5)
I believe the answer is:
admin
'start of a website manager's email address maybe' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for admin that I've seen before include "Paperwork (informal)" , "Business management" , "Form-filling (abbr.)" , "Back-office work (abbr)" , "Business organisers" .)