Article: key passage (5)
I believe the answer is:
aisle
'passage' is the definition.
(aisle can mean a path or passageway)
'article key' is the wordplay.
'article' becomes 'a' (the indefinite article in English).
'key' becomes 'isle' (I've seen this in another clue).
'a'+'isle'='AISLE'
(Other definitions for aisle that I've seen before include "Part of supermarket" , "Church walkway" , "Way between seat blocks" , "Passageway between seating areas" , "Passageway between pews" .)