Girl crashed hot rod approaching end of motorway (7)
I believe the answer is:
dorothy
'girl' is the definition.
'crashed hot rod approaching end of motorway' is the wordplay.
'crashed' indicates an anagram.
'approaching' says to put letters next to each other.
'end of' says to take the final letters.
The final letter of 'motorway' is 'y'.
'hot'+'rod'='hotrod'
'hotrod' anagrammed gives 'doroth'.
'doroth'+'y'='DOROTHY'
(Other definitions for dorothy that I've seen before include "Girl from Kansas" , "one of 5d's troupe" , "'Wizard of Oz' girl" , "Woman" , "Female" .)