Fed up with sexual vilifying (10)
I believe the answer is:
defamatory
'vilifying' is the definition.
(thesaurus)
'fed up with sexual' is the wordplay.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'with sexual' becomes 'amatory' (I can't explain this - if you can you should give a lot more credence to this answer).
'fed' in reverse letter order is 'def'.
'def'+'amatory'='DEFAMATORY'
Can you help me to learn more?
(Other definitions for defamatory that I've seen before include "Calumnious" , "Libellous" , "slanderous" , "insulting" , "abusive" .)