A fine yarn with a sadistic sound (6)
I believe the answer is:
crewel
'a fine yarn' is the definition.
'crewel' can be an answer for 'yarn' (I've seen this before). I'm unsure of the 'a fine' bit.
'a sadistic sound' is the wordplay.
'a sadistic' becomes 'cruel' (I've seen this in another clue).
'sound' shows a homophone (sound like).
'cruel' is a homophone of 'CREWEL'.
'with' acts as a link.
Can you help me to learn more?
(Other definitions for crewel that I've seen before include "Twisted yarn for tapestry or embroidery" , "Fine worsted yarn" .)