Food fanatic before term in stir (9)
I believe the answer is:
nutriment
'food' is the definition.
(nutriment is a kind of food)
'fanatic before term in stir' is the wordplay.
'fanatic' becomes 'nut' (I've seen this before).
'before' means one lot of letters go next to another.
'stir' indicates anagramming the letters.
'term'+'in'='termin'
'termin' is an anagram of 'riment'.
'nut'+'riment'='NUTRIMENT'
(Other definitions for nutriment that I've seen before include "It sustains" , "Material providing food" , "Sustenance, nourishment" , "Nourishing food" , "diet" .)