Bloomer in an auto race (9)
I believe the answer is:
carnation
'bloomer' is the definition.
(carnation is a kind of flowering plant)
'an auto race' is the wordplay.
'an auto' becomes 'car' ('car' can be a synonym of 'auto').
'race' becomes 'nation' (both can mean a national or ethnic group).
'car'+'nation'='CARNATION'
'in' is the link.
(Other definitions for carnation that I've seen before include "Flower suitable for buttonhole ..." , "Showy flower" , "Pink - garden flower" , "Oscar Wilde wore a green one" , "Anoint car with the strange flower" .)