Island dimness — last to leave house (5)
I believe the answer is:
igloo
'house' is the definition.
(I know that igloo is a type of house)
'island dimness last to leave' is the wordplay.
'island' becomes 'i' (geographical abbreviation).
'dimness' becomes 'gloom' (I've seen this in another clue).
'last to leave' means to remove the last letter.
'gloom' with its last letter removed is 'gloo'.
'i'+'gloo'='IGLOO'
(Other definitions for igloo that I've seen before include "Inuit dwelling" , "From domed hut" , "packed house" , "Eskimo's dwelling" , "Innuit dwelling" .)