Early stage of life (6)
I believe the answer is:
embryo
'early stage of life' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for embryo that I've seen before include "Early life form" , "It's potential to grow" , "Unborn offspring in the process of development" , "Fertilised human egg" , "Stage in development of unborn child" .)