Chilled, adding diamonds to diamonds (4)
I believe the answer is:
iced
'chilled' is the definition.
(icing is a kind of chilling)
'diamonds to diamonds' is the wordplay.
'diamonds' becomes 'ice' (slang term for diamonds).
'to diamonds' becomes 'd' (abbreviation in bridge say).
'ice'+'d'='ICED'
'adding' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for iced that I've seen before include "Decorated with frosting" , "found thus in freezer?" , "Glazed" , "Chilled; decorated" , "Kept cool" .)