Hate affecting excitement (4)
I believe the answer is:
heat
'excitement' is the definition.
(thesaurus)
'hate affecting' is the wordplay.
'affecting' indicates an anagram.
'hate' is an anagram of 'HEAT'.
(Other definitions for heat that I've seen before include "Cook" , "Energy that causes a rise in temperature" , "Level of spice" , "Preliminary race to qualify finalists" , "Get agitated" .)