Northern area set to change Lebanon’s region (4,4)
I believe the answer is:
near east
'lebanon's region' is the definition.
(I've seen this in another clue)
'northern area set to change' is the wordplay.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'to change' indicates anagramming the letters.
'area'+'set'='areaset'
'areaset' anagrammed gives 'eareast'.
'n'+'eareast'='NEAR EAST'
(Other definitions for near east that I've seen before include "The Balkans and Turkey" , "The Levant" , "where ancient civilisations developed" , "Region between India and the Mediterranean" , "SW Asia" .)