Polecat kin (6)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">polecat kin</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 ferret that I've seen before include "Diligent searcher" , "Assiduous searcher" , "Animal to hunt rats and rabbits" , "Small fierce animal - good hunting rabbits" , "Search about persistently" .)