Whistler, perhaps confined by police, disposing of diamonds (6)
I believe the answer is:
kettle
'whistler' is the definition.
(a kettle whistles when it boils)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for kettle that I've seen before include "Eurydice's husband" , "Drum and metal pot" , "Water boiler" , "Kitchen container and type of drum" , "Container for boiling water" .)