Necklace of spun carat gold breaks (4)
I believe the answer is:
torc
'necklace' is the definition.
(medieval neck ornament)
'spun carat gold breaks' is the wordplay.
'spun carat' becomes 'tc' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'gold' becomes 'or' ('or' is the heraldic name for gold).
'breaks' indicates putting letters inside.
'tc' enclosing 'or' is 'TORC'.
'of' is the link.
Can you help me to learn more?
(Other definitions for torc that I've seen before include "Metallic neck ornament" , "Rigid circular necklace" , "Choker" , "Celtic metal neck-ring" , "Metal armband worn by Ancient Britons" .)