Nosh cooked in unfinished hut on island (6)
I believe the answer is:
honshu
'island' is the definition.
(Honshu is an example)
'nosh cooked in unfinished hut' is the wordplay.
'cooked' indicates an anagram.
'in' is an insertion indicator.
'unfinished' means to remove the last letter.
'nosh' is an anagram of 'onsh'.
'hut' with its final letter removed is 'hu'.
'onsh' going into 'hu' is 'HONSHU'.
'on' acts as a link.
(Other definitions for honshu that I've seen before include "Japan's main island" , "The main island of Japan" , "Largest of the Japanese islands" , "The largest island unit of Japan" , "Largest island of Japanese mainland" .)