Thinnest and smallest eating nectarine's rind (7)
I believe the answer is:
leanest
'thinnest' is the definition.
('lean' is associated in meaning with 'thin')
'smallest eating nectarine's rind' is the wordplay.
'smallest' becomes 'least' (synonyms).
'eating' indicates putting letters inside.
'nectarine's rind' becomes 'ne' (I am not sure about this - if you are sure you should believe this answer much more).
'least' placed around 'ne' is 'LEANEST'.
'and' is the link.
Can you help me to learn more?
(Other definitions for leanest that I've seen before include "most meagre type" , "Least fatty" , "Poorest-quality" , "Least fat" , "Most thin" .)