Very boring dance party (5)
I believe the answer is:
revel
'party' is the definition.
(I've seen this before)
'very boring dance' is the wordplay.
'very' becomes 'v' (abbreviation).
'boring' is an insertion indicator (to bore something can mean to drill into it).
'dance' becomes 'reel' (reel is a kind of dance).
'v' inserted into 'reel' is 'REVEL'.
(Other definitions for revel that I've seen before include "Rejoice" , "Celebrate with a lever, strangely" , "Paint the town red" , "Riotous feast" , "Have a few drinks etc." .)