In Japan, move quickly and quietly ahead (6)

I believe the answer is:

nippon

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'in japan' is the definition.
'nippon' can be an answer for 'japan' (I've seen this in another clue). I am not certain of the 'in' bit.

'move quickly and quietly ahead' is the wordplay.
'move quickly' becomes 'ni' (I can't justify this - if you can you should give a lot more credence to this answer).
'and' means one lot of letters go next to another.
'quietly' becomes 'pp' (musical abbreviation for pianissimo).
'ahead' becomes 'on' (synonyms).
'ni'+'pp'+'on'='NIPPON'

Can you help me to learn more?

(Other definitions for nippon that I've seen before include "Transliteration of "Japan"" , "Japanese name for Japan (6)" .)

I've seen this clue in the Evening Standard.

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