Zigzag on skis (6)
I believe the answer is:
'zigzag on skis' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for slalom that I've seen before include "Downhill ski event" , "Skiers' obstacle race" , "Downhill ski race over a winding course" , "Downhill skiing race" , "Ski racing event" .)