Runner in a vigorous kind of winter sport (3)
I believe the answer is:
ski
This clue could be a double definition.
'runner in a vigorous kind' is the first definition.
'ski' can be an answer for 'runner' (something which 'runs', ie moves quickly on snow). I am unsure of the 'in a vigorous kind' bit.
'winter sport' is the second definition.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for ski that I've seen before include "Winter sports footwear" , "Slide downhill, sportingly" , "Type of snow shoe" , "Walk on snow" , "Move over snow on runners" .)