Water heater (6)
'water heater' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for boiler that I've seen before include "Device for heating water" , "Container to heat water or tough fowl" , "Water heater" , "Water-heater" , "tough old bird" .)
'water heater' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for kettle that I've seen before include "Water-boiler" , "In which to boil water or cook fish" , "Container for boiling water" , "Vessel for boiling water" , "Drum and metal pot" .)