Military raid (6)
I believe the answer is:
sortie
'military raid' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sortie that I've seen before include "Operational flight by a bomber or fighter" , "Sudden attack by besieged troops" , "Single military flight" , "Attack launched from place of siege" , "Military foray" .)