Hard to avoid publican in possibly obscene fraud (9)
I believe the answer is:
imposture
'fraud' is the definition.
(imposture is pretending to be someone else)
'hard to avoid publican in possibly obscene' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'to avoid' indicates named letters should be taken away.
'publican' becomes 'host' (I've seen this in other clues).
'in' is an insertion indicator.
'possibly obscene' becomes 'impure' (not pure or decent).
'host' with 'h' removed is 'ost'.
'ost' put inside 'impure' is 'IMPOSTURE'.
(Other definitions for imposture that I've seen before include "Trick" , "deception" , "The assuming of a false identity" , "Pretending to be another person" , "Fraud" .)