Vitellus (3,4)
(Other definitions for egg yolk that I've seen before include "What soldiers are dipped into" , "Omelette ingredient" , "Part of an ovum" , "17 [CAKE] ingredient" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">vitellus</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 yolk that I've seen before include "Yellow part of an egg" , "Part of a 7 Down" , "Egg's "yellow"" , "Yellow (as opposed to white?)" , "Soldiers go in here" .)