Can I turn around without energy? Not sure (9)

I believe the answer is:

uncertain

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'can i turn around without energy?' is the definition.
I can't tell whether this defines the answer.

'not sure' is the wordplay.
'not' becomes 'un' (I've seen this in other clues).
'sure' becomes 'certain' ('certain' can be a synonym of 'sure'**).
'un'+'certain'='UNCERTAIN'

Can you help me to learn more?

(Other definitions for uncertain that I've seen before include "Not convinced" , "Not completely confident or sure of" , "Not at all sure or decided" , "Lacking confidence" , "Not definitely known" .)

I've seen this clue in The Telegraph.

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