Mike too wary to travel by fast route (8)
I believe the answer is:
motorway
'fast route' is the definition.
(I've seen this before)
'mike too wary to travel' is the wordplay.
'mike' becomes 'M' (phonetic alphabet: alpha, bravo, charlie etc.).
'to travel' indicates anagramming the letters (I've seen 'travels' mean this).
'too'+'wary'='toowary'
'toowary' is an anagram of 'otorway'.
'm'+'otorway'='MOTORWAY'
'by' acts as a link.
(Other definitions for motorway that I've seen before include "High-speed highway" , "Fast road" , "In Germany, it's an autobahn" , "Autoroute" , "Major road" .)