Motion detector used up by climbers taking in summit of Nuptse (6)

I believe the answer is:

sensor

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'motion detector' is the definition.
'sensor' can be an answer for 'detector' ('sensor' can be a synonym of 'detector'). I am not certain of the 'motion' bit.

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for sensor that I've seen before include "Detection device" , "that could provide a smokescreen" , "Detector" , "Detecting device" , "device to detect change?" .)

I've seen this clue in the Irish Times and the Irish Times (Crosaire).

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