Passion in race (4)
I believe the answer is:
heat
I believe this is a double definition.
'passion' is the first definition.
('heat' can be a synonym of 'passion')
'race' is the second definition.
(I've seen this before)
'in' acts as a link.
(Other definitions for heat that I've seen before include "early round" , "Toast" , "Level of spice" , "It's measured in therms" , "Hotness" .)