Ruin race (4)
I believe the answer is:
dash
This clue is a double definition.
'ruin' is the first definition.
(thesaurus)
'race' is the second definition.
(dashing is a kind of racing)
(Other definitions for dash that I've seen before include "Run; lan" , "Go quickly" , "Drop" , "Striking" , "Pinch" .)