Clue: Japan referee lives in new hotel (7)
Answer: VARNISH
Explanation: Definition: Japan
 VAR(abbrev. for "Video Assistant Referee", in sports, an official who helps with the main referee's decision-making by reviewing the play on video recording) + IS(lives/exists) **contained in**(in) [ N(abbrev. for "new") + H(letter in the phonetic alphabet represented by "hotel") ].
Defn: Of which japan, a hard dark lacquer, is an example.