Fake concealed by skiers at Zermatt (6)
I believe the answer is:
ersatz
'fake' is the definition.
(ersatz means fake or imitation)
'concealed by skiers at zermatt' is the wordplay.
'concealed by' indicates the answer is hidden within the clue.
'ERSATZ' can be found hidden inside 'skiers at zermatt'.
(Other definitions for ersatz that I've seen before include "Mock" , "Made in imitation, from German" , "Imitation or substitute, from German" , "'Artificial, not genuine (6)'" , "Bogus" .)