Tiny bits of plastic are, in the end, creating unsightly waste (7)
I believe the answer is:
glitter
'tiny bits of plastic are in the end' is the definition.
I can't judge whether this definition defines the answer.
'unsightly waste' is the wordplay.
'unsightly' becomes 'g' (I can't justify this - if you can you should give a lot more credence to this answer).
'waste' becomes 'litter' (litter is a kind of waste).
'g'+'litter'='GLITTER'
'creating' is the link.
Can you help me to learn more?
(Other definitions for glitter that I've seen before include "addition to Christmas card" , "Flash" , "Twinkle" , "Sparkly decoration" , "Gleam" .)