Seating separator (5)
I believe the answer is:
'seating separator' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for aisle that I've seen before include "Supermarket passageway" , "Here comes the bride" , "Passage between seating areas" , "Passageway between blocks of seats" , "Church walkway" .)