Spoken of morality (4)
I believe the answer is:
oral
'spoken' is the definition.
(similar in meaning)
'of morality' is the wordplay.
'of' indicates a hidden word.
'ORAL' is hidden within 'morality'.
(Other definitions for oral that I've seen before include "Type of examination" , "By word of mouth (4)" , "Like some tradition" , "Mouth-related" , "Exam using speech" .)