Slight upset about Government late in the day (5)

I believe the answer is:

night

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'late in the day' is the definition.
I can't judge whether this defines the answer.

'slight upset about government' is the wordplay.
'slight' becomes 'thin' (similar in meaning).
'upset' says the letters should be written backwards.
'about' is an insertion indicator.
'government' becomes 'g' (abbreviation for government).
'thin' backwards is 'niht'.
'niht' enclosing 'g' is 'NIGHT'.

Can you help me to learn more?

(Other definitions for night that I've seen before include "Time without 10" , "Darkness; see you in the morning" , "follow-up to 16 [TWILIGHT]" , "Opposite of day" , "That's when it's darkest" .)

I've seen this clue in The Independent.

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