Len seems to have eaten some more fruit! (5)
I believe the answer is:
'fruit' is the definition.
(lemon is a kind of fruit)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for lemon that I've seen before include "Melon is another fruit" , "Tone" , "Melon (anag)" , "Something worthless" , "Dab" .)