Duck-billed creature (8)
I believe the answer is:
platypus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">duck-billed creature</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 platypus that I've seen before include "Primitive mammal, duck-billed" , "Duck-billed creature" , "Australian mammal with large bill and webbed feet" , "One's billed in flat manner" , "river creature" .)