Crackers I turn to in food processing (9)
I believe the answer is:
nutrition
'food processing' is the definition.
(process of obtaining nutrients)
'crackers i turn to in' is the wordplay.
'crackers' indicates an anagram (informal term for mad).
'i'+'turn'+'to'+'in'='iturntoin'
'iturntoin' with letters rearranged gives 'NUTRITION'.
(Other definitions for nutrition that I've seen before include "what's taken in?" , "form of sustenance" , "Food and drink, edibles" , "Food, its study" , "Food, nourishment" .)