Prop up; sustain (7)
I believe the answer is:
support
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">prop up</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >'<span class="explanation-format__original">sustain</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that sustain can be written as support)</span><br/ ><br/ ></span>
(Other definitions for support that I've seen before include "Maintain, back" , "strengthen" , "Help; bear" , "Shore up" , "second" .)