Amphibian larva (7)
I believe the answer is:
tadpole
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">amphibian larva</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 tadpole that I've seen before include "To plead for tiny frog" , "A frog-to-be" , "Larval form" , "Young toad" , "little swimmer" .)