Bloomer in motor race (9)
I believe the answer is:
carnation
'bloomer' is the definition.
(carnation is a kind of flowering plant)
'motor race' is the wordplay.
'motor' becomes 'car' (informal term for car).
'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 ..." , "Pink/white/red flower" , "Oscar Wilde wore a green one" , "Feature of many a wedding" , "Anoint car with the strange flower" .)