Company rescuer talked of sleepless period (5,5)

I believe the answer is:

white night

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'company rescuer talked' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'sleepless period' is the wordplay.
'sleepless' becomes 'white' (I can't explain this - if you can you should believe this answer much more).
'period' becomes 'night' (night is a kind of period).
'white'+'night'='WHITE NIGHT'

'of' acts as a link.

Can you help me to learn more?

I've seen this clue in The Times.

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