Cud (5)
I believe the answer is:
rumen
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">cud</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for rumen that I've seen before include "bit of guts (beastly type)" , "Place to digest" , "This organ" , "Cow's first stomach" , "First stomach of a cow - run me (anag)" .)