Long-tailed rodent (3)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">long-tailed rodent</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for rat that I've seen before include "Abandon" , "Plague-carrying rodent" , "One deserting sinking ship" , "Change sides" , "Scumbag" .)