Hostility, ill will (6)
I believe the answer is:
animus
I believe this clue is a double definition.
'hostility' is the first definition.
(I know that animus is a type of hostility)
'ill will' is the second definition.
(animus is a kind of ill will)
(Other definitions for animus that I've seen before include "Hostility, ill-feeling" , "Ill-feeling; hatred" , "spirit of hostility" , "Hostility shown in speech or action" , "Feeling of strong dislike" .)