Sloping surface (4)
I believe the answer is:
ramp
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sloping surface</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ramp that I've seen before include "Sloping path between levels" , "Change of level in road" , "Small ridge across a road - slow down" , "Slope - racket" , "Short slope" .)