Piece of biathlon equipment (3)
I believe the answer is:
ski
'piece of biathlon equipment' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ski that I've seen before include "Biathlon runner" , "Engage in a winter sport" , "Participate in winter sport" , "Descend fast" , "the end for many Russians" .)