Very serious complaint about student frolics (6)
I believe the answer is:
tragic
'very serious' is the definition.
'complaint about student frolics' is the wordplay.
'complaint' becomes 'tic' (a tic is a medical complaint).
'about' is an insertion indicator.
'student frolics' becomes 'rag' (I can't explain this - if you can you should give a lot more credence to this answer).
'tic' going around 'rag' is 'TRAGIC'.
Can you help me to learn more?
(Other definitions for tragic that I've seen before include "like King Lear" , "Very sad; Schubert's 4th symphony nickname" , "Characterised by extreme distress or sorrow" , "Extremely sad and distressing" , "Resulting in great loss" .)