Fruit for Wilhelm I, cutting into large one (5)
I believe the answer is:
lichi
'fruit' is the definition.
(lichi is a kind of fruit)
'wilhelm i cutting into large one' is the wordplay.
'wilhelm i' becomes 'ich' (I can't explain this - if you can you should give a lot more credence to this answer).
'cutting into' is an insertion indicator.
'large' becomes 'L' (eg in clothes sizes).
'one' becomes 'i' (Roman numeral).
'l'+'i'='li'
'ich' going within 'li' is 'LICHI'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for lichi that I've seen before include "Exotic fruit" , "(Chinese) fruit (tree)" .)