Young whale (4)
I believe the answer is:
calf
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">young whale</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 calf that I've seen before include "Young animal - part of leg" , "Is it above the ankle" , "Young moo-er" , "Animal that yields veal" , "Newborn cow" .)