Test right, scratching head (4)
I believe the answer is:
oral
'test' is the definition.
(oral is a type of examination)
'right scratching head' is the wordplay.
'right' becomes 'moral' (similar in meaning).
'scratching head' means to remove the first letter (the word\'s head is removed).
'moral' with its first letter removed is 'ORAL'.
(Other definitions for oral that I've seen before include "Mouth-related" , "Spoken exam" , "Via the mouth" , "Concerning the mouth" , "Viva voce" .)