Support from beneath (8)
I believe the answer is:
underpin
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">support from beneath</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 underpin that I've seen before include "buttress" , "Prop up with nun pride" , "corroborate" , "Support or strengthen from beneath" , "Form the basis for" .)