In Japan, it's possible to pop in at mid-morning (6)

I believe the answer is:

nippon

I'm a little stuck... Click here to teach me more about this clue!

'in japan' is the definition.
'nippon' can be an answer for 'japan' (I've seen this in another clue). I'm not sure about the 'in' bit.

I don't understand how the remainder of the clue works.

Can you help me to learn more?

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

I've seen this clue in the Evening Standard.

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