A French-built anti-ship missile (6)
I believe the answer is:
exocet
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">a french-built anti-ship missile</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 exocet that I've seen before include "Subsonic, low-altitude missile" , "Weapon" , "Short-range guided missile" , "Tactical missile" , "French missile used by Argentina in the Falklands War" .)