Embryonic protection in largely nominal form (6)
I believe the answer is:
amnion
'embryonic protection' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'largely nominal form' is the wordplay.
'largely' means to remove the last letter.
'form' is an anagram indicator.
'nominal' with its last letter taken away is 'nomina'.
'nomina' is an anagram of 'AMNION'.
'in' is the link.
Can you help me to learn more?
(Other definitions for amnion that I've seen before include "Innermost membrane" , "One embryo membrane" , "Film about site of early growth" .)