Lamb's remark about nan's fruit (6)
I believe the answer is:
banana
'fruit' is the definition.
(type of fruit)
'lamb's remark about nan's' is the wordplay.
'lamb's remark' becomes 'baa' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'baa' going around 'nan' is 'BANANA'.
(Other definitions for banana that I've seen before include "Long curved fruit" , "Fruit that comes in a bunch" , "Small politically unstable country dominated by foreign companies" , "that may be unzipped" , "Fruit grown in hands" .)