One wielding power behind the scenes, unpredictable in emergencies (8,5)

I believe the answer is:

eminence grise

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'one wielding power behind the scenes' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'unpredictable in emergencies' is the wordplay.
'unpredictable' is an anagram indicator.
'in'+'emergencies'='inemergencies'
'inemergencies' is an anagram of 'EMINENCE GRISE'.

Can you help me to learn more?

(Other definitions for eminence grise that I've seen before include "One exercising power in the background" , "Power behind the throne" .)

I've seen this clue in The Telegraph.

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