Night parties? Object! (5)
I believe the answer is:
thing
'object' is the definition.
(an object is a thing or item)
'night parties?' is the wordplay.
'parties?' indicates an anagram (the letters move or party around).
'night' is an anagram of 'THING'.
(Other definitions for thing that I've seen before include "Unspecified object" , "Night (anag)" , "Body" , "Inanimate object" , "Obsession" .)