Powder, to a skier (4)
I believe the answer is:
snow
'powder to a skier' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for snow that I've seen before include "Precipitation in the form of ice crystals" , "White Christmas requirement" , "Standard of whiteness" , "Flakes overhead" , "author" .)