A large protective coat for church table (5)
I believe the answer is:
altar
'church table' is the definition.
(ceremonial table in a church)
'a large protective coat' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'protective coat' becomes 'tar' (tar is used to coat roads).
'a'+'l'+'tar'='ALTAR'
'for' is the link.
(Other definitions for altar that I've seen before include "location for union negotiation" , "Table for sacrifice" , "Church focus for ritual" , "High table for religious ceremonies" , "Where we will vow" .)