Animus (3,4)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">animus</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ill will that I've seen before include "causing resentment" , "Hostility, malevolence" , "Bad feeling towards, hostility" , "Rancour" , "Animosity, hostile feeling" .)
(Other definitions for illwill that I've seen before include "Hatred" , "bad blood" .)