Barrage balloon (5)
I believe the answer is:
blimp
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">barrage balloon</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 blimp that I've seen before include "Airship - barrage balloon" , "Small barrage balloon" , "returns one pound to provost" , "Elderly pompous reactionary person" , "aircraft" .)