Ride west, for a change, which is most strange (8)
I believe the answer is:
weirdest
'is most strange' is the definition.
('weird' can be a synonym of 'strange')
'ride west for a change' is the wordplay.
'for a change' is an anagram indicator.
'ride'+'west'='ridewest'
'ridewest' with letters rearranged gives 'WEIRDEST'.
'which' acts as a link.
(Other definitions for weirdest that I've seen before include "Most uncanny!" , "Most unearthly" , "Most strikingly odd" , "Most bizarre" .)