Material that's down, note, in the market (6)
I believe the answer is:
angora
'material that's down' is the definition.
(angora is a downy material)
'note in the market' is the wordplay.
'note' becomes 'n' (abbreviation).
'in the' is an insertion indicator.
'market' becomes 'agora' (ancient Greek market area).
'n' going inside 'agora' is 'ANGORA'.
(Other definitions for angora that I've seen before include "Fur of rabbit - hair of goat" , "Yarn or fabric from hair of goats or rabbits" , "Yarn made from hair of goats or rabbits" , "Fabric from animal hair" , "Fabric made from goat or rabbit hair" .)