Examination relates to revolting content of popular opinion (4)
I believe the answer is:
oral
'examination' is the definition.
(oral is a kind of examination)
'revolting content of popular opinion' is the wordplay.
'revolting' shows that the letters should be reversed in order.
'content of' says the answer is hidden in the clue.
'laro' is hidden in the letters of 'popular opinion'.
'laro' written backwards gives 'ORAL'.
'relates to' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for oral that I've seen before include "Spoken - examination" , "Kind of exam" , "See 18" , "Via the mouth" , "Spoken test" .)