Cunning vehicle for winter trekkers primarily (7)
I believe the answer is:
sleight
'cunning' is the definition.
(I've seen this before)
'vehicle for winter trekkers primarily' is the wordplay.
'vehicle for winter' becomes 'sleigh'.
'primarily' suggests taking the first letters.
The initial letter of 'trekkers' is 't'.
'sleigh'+'t'='SLEIGHT'
(Other definitions for sleight that I've seen before include "Tricky cunning" , "Handy skill" , "Artful trick" , "Manual dexterity" , "It's deceiving to the eye" .)