White of an egg (7)
I believe the answer is:
albumen
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">white of an egg</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for albumen that I've seen before include "Egg-white" , "The white part of an egg" , "White poacher" , "Egg's white" .)