Temperature control of furthermost atmosphere (10)

I believe the answer is:

thermostat

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

'temperature control' is the definition.
'thermostat' can be an answer for 'control' (thermostat is a kind of control). I'm unsure of the 'temperature' bit.

'of furthermost atmosphere' is the wordplay.
'of' indicates the answer is hidden within the clue.
'THERMOSTAT' is hidden within 'furthermost atmosphere'.

Can you help me to learn more?

(Other definitions for thermostat that I've seen before include "Form of control" , "Heating device" , "Temperature regulator" , "Temperature controller" .)

I've seen this clue in The Telegraph.

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