Rich crumbly biscuit (10)
I believe the answer is:
shortbread
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">rich crumbly biscuit</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 shortbread that I've seen before include "Biscuit with plenty of butter" , "sweet but easily crumbling" , "Crumbly biscuit rich in butter" , "biscuits" , "Brittle buttery cake" .)