Which computer is a circuit-spinner? (6)

I believe the answer is:

laptop

I'm a little stuck... Click here to teach me more about this clue!

'which computer' is the definition.
I can't tell whether this defines the answer.

'circuit-spinner?' is the wordplay.
'circuit' becomes 'lap' (synonyms).
'spinner?' becomes 'top' (a spinning top).
'lap'+'top'='LAPTOP'

'is a' acts as a link.

Can you help me to learn more?

(Other definitions for laptop that I've seen before include "Small computer" , "Kind of computer" , "Portable computer" , "device?" , "Some work on this" .)

I've seen this clue in the Sydney Morning Herald.

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