Left in charge of first of obituary columns (7)
I believe the answer is:
Here is my best explanation:
'columns' is the definition.
'left in charge of first of obituary' is the subsidiary indication.
'left' becomes 'port' (left side of a ship - opposite of starboard).
'in charge of' becomes 'ic'.
'first of' indicates taking the first letters.
The initial letter of 'obituary' is 'o'.
(Other definitions for portico that I've seen before include "Elaborate porch", "series of columns", "small architectural feature", "Classical porch", "gallery, perhaps", "Colonnade in front of a building", "Roofed porch", "Zeno's teaching colonnade", "Grand entrance" and "Arcade".)