Swam around holding keys as they broadcast (7)

I believe the answer is:

webcams

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

'keys as they broadcast' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'swam around' is the wordplay.
I cannot really see how this works, but
'around' could be 'ca' (circa) and 'ca' is located in the answer.
This explanation may well be incorrect...

'holding' acts as a link.

Can you help me to learn more?

I've seen this clue in The Daily Express.

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