Possibly ten areas mostly in southwest Asia (4,4)
I believe the answer is:
near east
'southwest asia' is the definition.
(I've seen this in another clue)
'possibly ten areas' is the wordplay.
'possibly' indicates anagramming the letters.
'ten'+'areas'='tenareas'
'tenareas' with letters rearranged gives 'NEAR EAST'.
'mostly in' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for near east that I've seen before include "Iran and Iraq, etc" , "where communities are often in conflict" , "Region between India and the Mediterranean" , "SW Asia" , "where ancient civilisations developed" .)