Stair tread connector
I believe the answer is:
riser
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">stair tread connector</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 riser that I've seen before include "found on the staircase" , "Part of flight" , "Vertical piece between treads of staircase" , "Person getting out of bed" , "Upwardly mobile type" .)