Small airship or barrage balloon (5)
I believe the answer is:
blimp
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">small airship</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">barrage balloon</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for blimp that I've seen before include "aircraft" , "Small nonrigid airship" , "needs cover when shooting" , "Small barrage balloon" , "Pompous type - barrage balloon" .)