Support; pair (5)
I believe the answer is:
brace
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">support</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that brace is a type of structural member)</span><br/ ><br/ >'<span class="explanation-format__original">pair</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that pair can be written as brace)</span><br/ ><br/ ></span>
(Other definitions for brace that I've seen before include "Strengthening piece" , "Support - pair" , "Pair - strut" , "prepare for impact" , "Support; two" .)