Sure to be upset following party conversation (9)
I believe the answer is:
discourse
'conversation' is the definition.
(thesaurus)
'sure to be upset following party' is the wordplay.
'to be upset' is an anagram indicator.
'following' says to put letters next to each other.
'party' becomes 'disco' (I've seen this before**).
'sure' anagrammed gives 'urse'.
'urse' put after 'disco' is 'DISCOURSE'.
(Other definitions for discourse that I've seen before include "Conversation, dialogue" , "Written or spoken communication" , "verbal communication" , "Formal discussion of a topic" , "Speech - conversation" .)