I turn bananas into processed food (9)
I believe the answer is:
nutrition
'food' is the definition.
(I know that nutrition is a type of food)
'i turn bananas into processed' is the wordplay.
'bananas' indicates anagramming the letters (bananas can informally mean crazy).
'processed' indicates anagramming the letters.
'i'+'turn'='iturn'
'iturn' anagrammed gives 'nutri'.
'into' with letters rearranged gives 'tion'.
'nutri'+'tion'='NUTRITION'
(Other definitions for nutrition that I've seen before include "Food, its study" , "Act of nourishing" , "what's taken in?" , "Food and drink, edibles" , "form of sustenance" .)