For example, copper kettle has one (7)
I believe the answer is:
element
This clue is a double definition.
'for example copper' is the first definition.
(copper is a chemical element)
'kettle has one' is the second definition.
(electrical component)
(Other definitions for element that I've seen before include "He, say" , "Iron, for instance - part of an electric kettle" , "Fire (or part of one)" , "Constituent component" , "Component - factor" .)