Runner from Donetsk indisposed (3)
I believe the answer is:
ski
'runner' is the definition.
(something which 'runs', ie moves quickly on snow)
'from donetsk indisposed' is the wordplay.
'from' indicates the answer is hidden within the clue.
'SKI' is hidden within 'donetsk indisposed'.
(Other definitions for ski that I've seen before include "Biathlon runner" , "Sport on piste" , "Winter sports footwear" , "Narrow runner for snow and water" , "Journey" .)