Challenge on the slopes (5)
I believe the answer is:
mogul
'challenge on the slopes' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mogul that I've seen before include "Mr Big?" , "big shot" , "Tycoon -- ski slope mound" , "Former Indian ruler; bump on a ski slope" , "Powerful man" .)