Steer without crashing hot-rod, as is customary (8)
I believe the answer is:
orthodox
'is customary' is the definition.
(thesaurus)
'steer without crashing hot-rod' is the wordplay.
'steer' becomes 'ox'.
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'crashing' indicates anagramming the letters.
'hot'+'rod'='hotrod'
'hotrod' anagrammed gives 'rthodo'.
'ox' going around 'rthodo' is 'ORTHODOX'.
'as' acts as a link.
(Other definitions for orthodox that I've seen before include "Conforming with established doctrine" , "Conformist" , "Adhering to what is commonly accepted" , "Traditional" , "Conforming to the accepted beliefs of a religion" .)