Indecent milieu and activities of former pupils? (7)
I believe the answer is:
obscene
'indecent' is the definition.
(similar in meaning)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for obscene that I've seen before include "Improper" , "X-rated" , "Indecent or pornographic" , "off colour?" , "coarse!" .)