Works in mill briefly, making lustrous thread for fabric (8)
I believe the answer is:
silkworm
'works in mill briefly' is the definition.
I can't judge whether this definition defines the answer.
'lustrous thread for fabric' is the wordplay.
'lustrous thread' becomes 'worm' (I can't explain this - if you can you should give a lot more credence to this answer).
'for' says to put letters next to each other (I've seen this in other clues).
'fabric' becomes 'silk' (silk is a kind of fabric).
'worm' after 'silk' is 'SILKWORM'.
'making' is the link.
Can you help me to learn more?
(Other definitions for silkworm that I've seen before include "It feeds on mulberry leaves" , "Caterpillar yielding fine fibre" , "It feeds on the 24" .)