Layer of green eggs (3)
I believe the answer is:
emu
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">layer of green eggs</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for emu that I've seen before include "Australian bird related to the ostrich" , "one offering challenge to Hull?" , "Flightless Aus. bird" , "Australian non-flyer" , "Flightless bird of Australia, like ostrich" .)