Test of right and left, originally (4)
I believe the answer is:
oral
'test' is the definition.
(oral is a type of examination)
'of right and left originally' is the wordplay.
'originally' indicates taking the first letters.
The initial letters of 'of right and left' is 'ORAL'.
(Other definitions for oral that I've seen before include "Concerning the mouth" , "Spoken test" , "Spoken exam" , "Kind of exam" , "Type of exam" .)