Hush! No trouble in this part of Japan (6)
I believe the answer is:
honshu
'this part of japan' is the definition.
('Honshu' is part of 'japan')
'hush no trouble' is the wordplay.
'trouble' indicates anagramming the letters.
'hush'+'no'='hushno'
'hushno' is an anagram of 'HONSHU'.
'in' acts as a link.
(Other definitions for honshu that I've seen before include "Largest of the islands forming Japan" , "Largest of the four main islands of Japan" , "Japan's main island" , "Largest island of Japanese mainland" , "part of Japan" .)