Layer of green eggs (3)
I believe the answer is:
emu
'layer of green eggs' is the definition.
(I've seen this in another clue)
This is the entire clue.
(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" .)