Window alternative (5)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">window alternative</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for aisle that I've seen before include "Passage between rows of seats" , "Church walkway" , "way for prospective union members?" , "channel" , "Path between seats in church" .)