Conversation in nightclub sure ridiculous! (9)
I believe the answer is:
discourse
'conversation' is the definition.
(thesaurus)
'nightclub sure ridiculous' is the wordplay.
'nightclub' becomes 'disco' (I've seen this before).
'ridiculous' is an anagram indicator.
'sure' with letters rearranged gives 'urse'.
'disco'+'urse'='DISCOURSE'
'in' acts as a link.
(Other definitions for discourse that I've seen before include "(Formal) talk" , "Speech - conversation" , "Conversation, dialogue" , "Written or spoken communication" , "To hold a conversation" .)