"I do" site (5)
I believe the answer is:
altar
'i do site' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for altar that I've seen before include "location for union negotiation" , "Sacrifical stone sounds as if it will change" , "Sacrificial table" , "Place for sacrifices" , "High table for religious ceremonies" .)