Academic, finding article filthy, on occasion, indicates obscenity (9)
I believe the answer is:
profanity
'obscenity' is the definition.
(thesaurus)
'academic finding article filthy on occasion' is the wordplay.
'academic' becomes 'prof' (short for professor).
'finding' is a charade indicator (letters next to each other).
'article' becomes 'an' (indefinite article).
'on occasion' means one should take alternating letters.
The alternate letters of 'filthy' are 'ity'.
'prof'+'an'+'ity'='PROFANITY'
'indicates' acts as a link.
(Other definitions for profanity that I've seen before include "Blasphemous language" , "Irreverence" , "Expletive" , "Oath" , "Four-letter word" .)