Ancient Greek portico some confess to admiring (4)
I believe the answer is:
stoa
'ancient greek portico' is the definition.
(I've seen this before)
'some confess to admiring' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'STOA' is hidden within 'confess to admiring'.
(Other definitions for stoa that I've seen before include "Roofed colonnade (Gr.)" , "old school" , "Covered walk with colonnade" , "Roofed walkway with colonnades - oats (anag)" , "Where Zeno spoke" .)