Soft casing of lead could often conserve our old nectarines (6)
I believe the answer is:
cocoon
'soft casing' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'of lead could often conserve our old nectarines' is the wordplay.
'of lead' says to take the initial letters (I've seen 'leading' mean this).
The first letters of 'could often conserve our old nectarines' is 'COCOON'.
Can you help me to learn more?
(Other definitions for cocoon that I've seen before include "Protective cover of silkworms, etc" , "Envelop for protection" , "Protective case for insect" , "Protection for pupa" , "Chrysalis casing" .)