Hate turning agent about nothing (6)
I believe the answer is:
loathe
'hate' is the definition.
(I know that loathe is a more specific form of the action hate)
'turning agent about nothing' is the wordplay.
'turning agent' becomes 'lathe' (a lathe is used to turn things).
'about' indicates putting letters inside.
'nothing' becomes 'O' (O resembles 0).
'lathe' placed around 'o' is 'LOATHE'.
(Other definitions for loathe that I've seen before include "Abhor, execrate" , "Hate (someone)" , "Find disgusting" , "Dislike intensely" , "Feel disgust for (person)" .)