Mount for finest journey (8)
I believe the answer is:
bestride
'mount' is the definition.
(I know that mount can be written as bestride)
'finest journey' is the wordplay.
'finest' becomes 'best' (similar in meaning).
'journey' becomes 'ride' (riding is a kind of journeying).
'best'+'ride'='BESTRIDE'
'for' is the link.
(Other definitions for bestride that I've seen before include "span" , "get a legover?" , "Get across" , "Mounted" , "Stand across" .)