Test of right and left, all characters on the far left (4)
I believe the answer is:
oral
'test' is the definition.
(oral is a type of examination)
'of right and left all characters on the far left' is the wordplay.
'all characters on the far left' indicates taking the first letters (letters on the left ends of the words).
The initial letters of 'of right and left' is 'ORAL'.
(Other definitions for oral that I've seen before include "By word of mouth, like some exams" , "By word of mouth (4)" , "Spoken, of the mouth" , "Relating to speech" , "'Spoken, not written (4)'" .)