Inflatable rubber bag (7)
I believe the answer is:
balloon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">inflatable rubber bag</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 balloon that I've seen before include "Brandy glass" , "Bag filled with gas or air" , "Inflatable - rapidly expand" , "Inflate" , "Air-filled bag" .)