Shiny stuff -- no good -- rubbish! (6)
I believe the answer is:
litter
'rubbish' is the definition.
(litter is a kind of rubbish)
'shiny stuff no good' is the wordplay.
'shiny stuff' becomes 'glitter' (shiny substance or material).
'no' indicates named letters should be taken away.
'good' becomes 'g' (abbreviation).
'glitter' with 'g' taken away is 'LITTER'.
(Other definitions for litter that I've seen before include "Rubbish left lying about in public" , "Clean up the canine offspring?" , "untidiness" , "Bits of rubbish left lying about" , "Brood of young born to an animal" .)