Food I turn into stew … (9)
I believe the answer is:
nutrition
'food' is the definition.
(I've seen this before)
'i turn into stew' is the wordplay.
'stew' indicates an anagram.
'i'+'turn'+'into'='iturninto'
'iturninto' with letters rearranged gives 'NUTRITION'.
(Other definitions for nutrition that I've seen before include "what's taken in?" , "Food, its study" , "Food and drink, edibles" , "Food, nourishment" , "Act of nourishing" .)