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" .)

I've seen this clue in The Times.

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