Rejecting uncooked food results in hostility (7)
I believe the answer is:
warfare
'hostility' is the definition.
(thesaurus)
'rejecting uncooked food' is the wordplay.
'rejecting' says the letters should be written in reverse.
'uncooked' becomes 'raw' (similar in meaning).
'food' becomes 'fare' (fare is a kind of food).
'raw' reversed gives 'war'.
'war'+'fare'='WARFARE'
'results in' acts as a link.
(Other definitions for warfare that I've seen before include "Scraps, too, by the look of it" , "Strife" , "Armed conflict" , "action" , "All-out fighting" .)