Driving test obstacle (4)
I believe the answer is:
cone
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">driving test obstacle</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for cone that I've seen before include "Hollow object associated with ice cream and motorways" , "16 Cornet" , "standing in middle of motorway" , "Volcanic peak" , "Dry fruit of many evergreen trees, say pine" .)