Acrobat's wire (9)
I believe the answer is:
tightrope
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">acrobat's wire</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 tightrope that I've seen before include "Acrobat's walkway" , "High wire" , "Difficult thing to walk on" , "Acrobat's wire" , "An acrobat walks on this high above the ground" .)