Best available vehicles for reversing (8)
I believe the answer is:
outsmart
'best' is the definition.
(outsmarting is a kind of besting)
'available vehicles for reversing' is the wordplay.
'available' becomes 'out' (as in a product which is out).
'vehicles' becomes 'trams' (tram is a kind of vehicle).
'for reversing' says the letters should be written in reverse.
'trams' back-to-front is 'smart'.
'out'+'smart'='OUTSMART'
(Other definitions for outsmart that I've seen before include "Best" , "Cunningly get the better of" , "Outmanoeuvre cleverly" , "Excel in cleverness" , "Defeat by skillful maneuvering" .)