Intensity of feeling produced by race (4)
I believe the answer is:
heat
I believe this clue is a double definition.
'intensity of feeling' is the first definition.
(I've seen this in another clue)
'race' is the second definition.
(I know that heat is a type of race)
'produced by' is the link.
(Other definitions for heat that I've seen before include "brings out a sweat?" , "Raise temperature" , "Vehemence" , "It's measured in therms" , "eliminating round" .)