Atrocious standard set by harangue (8)
I believe the answer is:
flagrant
'atrocious' is the definition.
(thesaurus)
'standard set by harangue' is the wordplay.
'standard' becomes 'flag' (I've seen this in another clue).
'set by' is a charade indicator (letters next to each other).
'harangue' becomes 'rant' (synonyms).
'flag'+'rant'='FLAGRANT'
(Other definitions for flagrant that I've seen before include "Of unconcealed outrageousness" , "Very bad and obvious, say offence" , "Blatant, outrageous" , "Conspicuous, blatant" , "Unashamed" .)