Car revealing nothing right on test (5)
I believe the answer is:
motor
'car' is the definition.
(thesaurus)
'nothing right on test' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'right' becomes 'r' (common abbreviation).
'on' means one lot of letters go next to another.
'test' becomes 'mot' (**).
'o'+'r'='or'
'or' put after 'mot' is 'MOTOR'.
'revealing' acts as a link.
(Other definitions for motor that I've seen before include "Engine - relating to movement" , "Car (colloq,)" , "Make good progress" , "Car (informal)" , "Move quickly" .)