Accomplices hiding diamonds (3)
I believe the answer is:
ice
'diamonds' is the definition.
(slang term for diamonds)
'accomplices hiding' is the wordplay.
'hiding' indicates a hidden word.
'ICE' can be found hidden inside 'accomplices'.
(Other definitions for ice that I've seen before include "It's cold and slippy" , "To put in a drink or slide on" , "A state of water" , "Frozen water; kill (slang)" , "Reserve" .)