Go downhill (5)
I believe the answer is:
slide
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">go downhill</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for slide that I've seen before include "Playground chute" , "that's put under the microscope" , "Playground structure" , "leading to a fall" , "Microscope glass" .)