NW state unfortunately ends with black lava (6)
I believe the answer is:
alaska
'nw state' is the definition.
(most northwestern state of the US)
'unfortunately ends with black lava' is the wordplay.
'unfortunately' becomes 'alas' ('alas' is used to express regret).
'ends with' suggests the final letters (the ends of the words).
The last letters of 'black lava' are 'ka'.
'alas'+'ka'='ALASKA'
(Other definitions for alaska that I've seen before include "Sarah Palin's home state" , "Largest US state by area" , "49th US state" , "Anchorage location" , "Most northerly US state" .)