Lean to one side and sneer, agitating the audience (9)
I believe the answer is:
listeners
'audience' is the definition.
(people listening to something)
'lean to one side and sneer agitating' is the wordplay.
'lean to one side' becomes 'list' (I've seen this in another clue).
'and' means one lot of letters go next to another.
'agitating' indicates an anagram.
'sneer' anagrammed gives 'eners'.
'list'+'eners'='LISTENERS'
'the' acts as a link.
(Other definitions for listeners that I've seen before include "Those who pay attention" , "radio enthusiasts" , "Those who hear" , "Hearers" , "They follow advice" .)