Study O-Level Sociology essentially from the beginning (2,4)

I believe the answer is:
de novo
'from the beginning' is the definition.
(I've seen this in another clue)
'study o-level sociology essentially' is the wordplay.
'study' becomes 'den' (term for a study or office).
'o-level' becomes 'ov' (I can't explain this - if you can you should give a lot more credence to this answer).
'essentially' indicates the central letters.
The middle of 'sociology' is 'o'.
'den'+'ov'+'o'='DE NOVO'
Can you help me to learn more?
(Other definitions for de novo that I've seen before include "Anew (Latin)" , "Once more, again - in Latin phrase" , "afresh" , "From scratch" .)
