Speak evil about none (5)
I believe the answer is:
voice
'speak' is the definition.
(thesaurus)
'evil about none' is the wordplay.
'evil' becomes 'vice' (vice is a kind of evil).
'about' is an insertion indicator.
'none' becomes 'o'.
'vice' placed around 'o' is 'VOICE'.
(Other definitions for voice that I've seen before include "Spoken sound" , "Power of speaking" , "Opinion; express in words" , "Give expression to" , "Wallop" .)