Greek market stocking new yarn (6)
I believe the answer is:
angora
'yarn' is the definition.
(angora is a type of yarn)
'greek market stocking new' is the wordplay.
'greek market' becomes 'agora' (agoras were market spaces in ancient Greece).
'stocking' means one lot of letters goes inside another ('stock' can mean 'carry' or 'contain').
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'agora' placed around 'n' is 'ANGORA'.
(Other definitions for angora that I've seen before include "Fine yarn from hair of goats" , "Goat producing mohair" , "Fine wool from certain goats" , "Soft yarn from certain goats" , "Cloth from the soft hair of a goat" .)