Operational flight (6)
I believe the answer is:
sortie
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">operational flight</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for sortie that I've seen before include "Short foray" , "Single military flight" , "Military aircraft's flight" , "Attack by a besieged garrison" , "Military foray" .)