Switch on metric paging system (8)

I believe the answer is:

intercom

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'system' is the definition.
(intercom is a kind of system)

'switch on metric' is the wordplay.
'switch' indicates an anagram.
'on'+'metric'='onmetric'
'onmetric' anagrammed gives 'INTERCOM'.

'paging' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.

Can you help me to learn more?

(Other definitions for intercom that I've seen before include "System of communication often on door" , "Means of transmitting messages" , "way to communicate" , "Receiver" , "Short-range telephone system" .)

I've seen this clue in The Telegraph.

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