Sewer rodent (3)
I believe the answer is:
rat
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sewer rodent</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 rat that I've seen before include "person doing shopping" , "Inform" , "Contemptible person" , "Scumbag" , "Desert - rodent" .)