Tincture spilt in a car (6)
I believe the answer is:
arnica
'tincture' is the definition.
(arnica is a kind of tincture)
'spilt in a car' is the wordplay.
'spilt' indicates anagramming the letters.
'in'+'a'+'car'='inacar'
'inacar' anagrammed gives 'ARNICA'.
(Other definitions for arnica that I've seen before include "Plant - preparation used for treating bruises" , "Ointment used to treat bruises" , "Tincture of mountain tobacco, good for bruises, etc" , "flowering plant" , "Herb used for treating bruises" .)