Loathing in that event (4)
I believe the answer is:
hate
'loathing' is the definition.
(thesaurus)
'in that event' is the wordplay.
'in' says the answer is hidden in the clue.
'HATE' can be found hidden inside 'that event'.
(Other definitions for hate that I've seen before include "Fury" , "Passion" , "Passionately dislike" , "'Unimaginable as ---- in Heav'n': Milton" , "powerful emotion" .)