Apprehensive over bursting into sunrise (7)

I believe the answer is:

nervous

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'apprehensive' is the definition.
(synonyms)

'over bursting into sunrise' is the wordplay.
'bursting' indicates an anagram.
'into' indicates putting letters inside.
'sunrise' becomes 'nus' (I can't justify this - if you can you should give a lot more credence to this answer).
'over' anagrammed gives 'ervo'.
'ervo' placed within 'nus' is 'NERVOUS'.

Can you help me to learn more?

(Other definitions for nervous that I've seen before include "Agitated and apprehensive" , "full of trepidation" , "stewing" , "Highly strung" , "Feeling or showing anxiety" .)

I've seen this clue in The Globe and Mail.

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