Biathlete's need (3)
I believe the answer is:
ski
'biathlete's need' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ski that I've seen before include "Hit the slopes" , "Glide ove snow" , "Slide on snow" , "Move over snow or water" , "Descend fast" .)