Hubble-bubble (6)
I believe the answer is:
hookah
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">hubble-bubble</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for hookah that I've seen before include "Smoking pipe, using water" , "Oriental water pipe for smoking" , "Pipe for smoking marijuana etc" , "A pipe; sounds like a rugby position" , "Sort of pipe" .)