Traces piece of glass, e.g. -- it's eventually returned (8)
I believe the answer is:
vestiges
'traces' is the definition.
('vestige' can be a synonym of 'trace')
'of glass e g it's eventually returned' is the wordplay.
'of' indicates the answer is hidden within the clue.
'returned' says the letters should be written in reverse.
'segitsev' can be found hidden inside 'glass e g its eventually'.
'segitsev' reversed gives 'VESTIGES'.
'piece' acts as a link.
(Other definitions for vestiges that I've seen before include "Surviving traces" , "Remnants" .)