Crack shot, one from Southern Asia (7)
I believe the answer is:
punjabi
'from southern asia' is the definition.
(the Punjab is a Southern Asian region)
'crack shot one' is the wordplay.
'crack' becomes 'pun' (crack can mean a joke).
'shot' becomes 'jab' (both can mean an injection).
'one' becomes 'i' (Roman numeral).
'pun'+'jab'+'i'='PUNJABI'
(Other definitions for punjabi that I've seen before include "Language spoken in an area between Pakistan and India" , "Subcontinental language" , "Eastern language" , "foreign language" , "tongue" .)