A Whistler in the kitchen? (6)
I believe the answer is:
kettle
'a whistler' is the definition.
(a kettle whistles when it boils)
I don't understand how the rest of the clue works.
(Other definitions for kettle that I've seen before include "Container for boiling water" , "Contain demonstrators" , "Kitchen boiler?" , "Vessel for boiling water" , "One called black by pot" .)