Play around in floor in Japan (5)
I believe the answer is:
kyoto
'in japan' is the definition.
('Kyoto' is part of 'japan')
'play around in floor' is the wordplay.
'play' becomes 'toy' (synonyms).
'around' says the letters should be written backwards.
'in' means one lot of letters goes inside another.
'floor' becomes 'ko' (I've seen this in other clues).
'toy' written backwards gives 'yot'.
'yot' going within 'ko' is 'KYOTO'.
(Other definitions for kyoto that I've seen before include "Japanese city of treaty on climate change" , "Japan's old capital" , "Old Japanese capital" , "Tokyo (anag) - former capital of Japan" , "Former Japanese capital city - Tokyo (anag)" .)