Inquest briefly rubbished Glitter disc? (6)
I believe the answer is:
sequin
'glitter disc?' is the definition.
'inquest briefly rubbished' is the wordplay.
'briefly' means to remove the last letter.
'rubbished' indicates anagramming the letters.
'inquest' with its final letter removed is 'inques'.
'inques' with letters rearranged gives 'SEQUIN'.
(Other definitions for sequin that I've seen before include "Small shiny disc for decoration" , "Small shiny disc on a garment" , "Italian gold coin" , "Ballroom dancer's sewn-on sparkler?" , "Shiny piece to decorate garment" .)