Response to Racine mixed (8)
I believe the answer is:
reaction
'response' is the definition.
(synonyms)
'to racine mixed' is the wordplay.
'mixed' is an anagram indicator.
'to'+'racine'='toracine'
'toracine' with letters rearranged gives 'REACTION'.
(Other definitions for reaction that I've seen before include "Reflex; backlash" , "Into care (anag)" , "Feedback" , "Answer" , "Chemical change or backlash" .)