Egg hatcher (9)
I believe the answer is:
incubator
'egg hatcher' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for incubator that I've seen before include "Apparatus for hatching eggs" , "Artificial substitute for a hen's warmth" , "Egg hatching apparatus" , "hospital equipment" , "Promotor of growth" .)