It's small and green like some unripe apples (3)
I believe the answer is:
pea
'it's small and green' is the definition.
I can't tell whether this defines the answer.
'some unripe apples' is the wordplay.
'some' indicates the answer is hidden within the clue (some parts of the word are used).
'PEA' can be found hidden inside 'unripe apples'.
'like' acts as a link.
Can you help me to learn more?
(Other definitions for pea that I've seen before include "Edible seed from pod" , "Seed eaten as vegetable" , "veg" , "Annual climbing plant with edible seeds" , "garden plant" .)