Live in retreat — most mean (7)
I believe the answer is:
dearest
'mean' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'live in retreat most' is the wordplay.
'live in' becomes 'dear' (I can't explain this - if you can you should give a lot more credence to this answer).
'retreat' becomes 'nest' (nest is a kind of retreat).
'most' means to remove the first letter.
'nest' with its initial letter removed is 'est'.
'dear'+'est'='DEAREST'
Can you help me to learn more?
(Other definitions for dearest that I've seen before include "Most precious or expensive" , "Most expensive or beloved" , "The beloved one is most costly" , "Loved one" , "Most loved or expensive" .)