Second bar rejected parties (6)
I believe the answer is:
revels
'parties' is the definition.
(I've seen this before)
'second bar rejected' is the wordplay.
'second' becomes 's' (common abbreviation).
'bar' becomes 'lever' (lever is a kind of bar).
'rejected' says the letters should be written in reverse.
's'+'lever'='slever'
'slever' backwards is 'REVELS'.
(Other definitions for revels that I've seen before include "Celebrations with levers" , "Parties" , "Merrymaking" , "Noisy celebrations" , "Has great fun with levers" .)