Bully's empty attempt to harangue (6)
I believe the answer is:
tyrant
'bully's' is the definition.
(thesaurus)
'empty attempt to harangue' is the wordplay.
'empty' says to hollow out the word (remove centre letters).
'attempt' becomes 'try' (I've seen this before).
'to harangue' becomes 'rant' ('rant' can be a synonym of 'harangue').
'try' with its middle taken out is 'ty'.
'ty'+'rant'='TYRANT'
(Other definitions for tyrant that I've seen before include "Authoritarian" , "Despot, dictator" , "Cruel and oppressive dictator" , "bully - with 17d" , "Oppressor" .)