Arid region: I've found it right in middle of South Africa (6)
I believe the answer is:
sahara
'arid region' is the definition.
'i've found it right in middle of south africa' is the wordplay.
'i've found it' becomes 'aha' (exclamation said after finding something).
'right' becomes 'r' (common abbreviation).
'in middle of' indicates putting letters inside.
'south africa' becomes 'sa' (abbreviation).
'aha'+'r'='ahar'
'ahar' placed inside 'sa' is 'SAHARA'.
(Other definitions for sahara that I've seen before include "Uncultivated region of north Africa" , "About 3,500,000 square miles of Africa" , "Hottest desert" , "World's largest sandy area" , "Great African desert" .)