Diamonds: diamonds get you murdered! (4)
I believe the answer is:
iced
'murdered' is the definition.
(ice can informally mean to murder)
'diamonds diamonds' is the wordplay.
'diamonds' becomes 'ice' (slang term for diamonds).
'diamonds' becomes 'd' (abbreviation for the card suit diamonds).
'ice'+'d'='ICED'
'get you' is the link.
I am not very happy about this link. Some or all of 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 "Chilled - killed" , "Decorated; killed" , "hidden under white crystals?" , "Frozen, chilled" , "Decorated with sugary mixture" .)