Unconventional intellectual, abandoned by university, has cut Charlie off for being a snitch (8)
I believe the answer is:
telltale
'a snitch' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for telltale that I've seen before include "One spreads other people's secrets" , "Person who blabs or something that reveals" , "One revealing secrets" , "Outward indication of something concealed" , "Revealer of secrets" .)