Journey by air (6)
I believe the answer is:
flight
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">journey by air</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for flight that I've seen before include "Attachment to missile < part of Air Force" , "Air force unit; running away" , "Stairs; escape" , "Journey made by plane" , "Set of stairs" .)