Left religious painting unfinished that's covered entrance (7)
I believe the answer is:
portico
'covered entrance' is the definition.
(I've seen this before)
'left religious painting unfinished' is the wordplay.
'left' becomes 'port' (left side of a ship - opposite of starboard).
'religious painting' becomes 'icon' (I've seen this before).
'unfinished' means to remove the last letter.
'icon' with its last letter taken off is 'ico'.
'port'+'ico'='PORTICO'
'that's' acts as a link.
(Other definitions for portico that I've seen before include "Grand entrance" , "Zeno's teaching colonnade" , "Covered porch with supporting columns" , "Arcade" , "Colonnade in front of a building" .)