Send first charmer away then lose interest (6,3)

I believe the answer is:

switch off

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'then lose interest' is the definition.
I can't judge whether this defines the answer.

'send first charmer away' is the wordplay.
'send first' becomes 's' (1st letter of 'send').
'charmer' becomes 'witch' (someone who charms).
'away' becomes 'off' (synonyms).
's'+'witch'+'off'='SWITCH OFF'

Can you help me to learn more?

(Other definitions for switch off that I've seen before include "Lose concentration" , "Stop paying attention" , "Disconnect power" .)

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

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