Fourfold (9)
I believe the answer is:
quadruple
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fourfold</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for quadruple that I've seen before include "Increase fourfold" , "Times by four" , "Multiply by two, twice" .)