Military mission (6)
I believe the answer is:
sortie
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">military mission</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 sortie that I've seen before include "Military aircraft's flight" , "Military aircraft flight" , "Raid - short trip" , "Breakout by besieged garrison" , "Operational flight by a bomber or fighter" .)