Award of supersized vehicle (5)
I believe the answer is:
oscar
'award' is the definition.
(Academy Award)
'supersized vehicle' is the wordplay.
'supersized' becomes 'os' (short for oversize).
'vehicle' becomes 'car' (car is a kind of vehicle).
'os'+'car'='OSCAR'
'of' is the link.
(Other definitions for oscar that I've seen before include "Librettist Hammerstein, d. 1960" , "Note" , "- - Peterson, pianist" , "Film award; --- Hammerstein" , "Statuette awarded by Hollywood Academy" .)