Some spectators killed runner (3)
I believe the answer is:
ski
'runner' is the definition.
(something which 'runs', ie moves quickly on snow)
'some spectators killed' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'SKI' is hidden in the letters of 'spectators killed'.
(Other definitions for ski that I've seen before include "Descend fast" , "Snow blade" , "Slide downhill, sportingly" , "Journey" , "Winter-sports item" .)