Bovine spongiform encephalopathy (3,3,7)
I believe the answer is:
mad cow disease
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bovine spongiform encephalopathy</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 mad cow disease that I've seen before include "BSE (colloq.)" , "killer" , "Bovine spongiform encephalopathy" , "Beastly ailment" .)