Armed helicopter (7)
I believe the answer is:
gunship
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">armed helicopter</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for gunship that I've seen before include "Military aircraft" , "Armed vessel" , "Heavily armed helicopter" .)