Simplistic and muddled again about old part of South America (9)
I believe the answer is:
patagonia
'part of south america' is the definition.
(I know that Patagonia is part of Argentina)
'simplistic and muddled again about old' is the wordplay.
'simplistic' becomes 'pat' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' says to put letters next to each other.
'muddled' is an anagram indicator.
'about' indicates putting letters inside.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'again' with letters rearranged gives 'agnia'.
'agnia' enclosing 'o' is 'agonia'.
'pat'+'agonia'='PATAGONIA'
Can you help me to learn more?
(Other definitions for patagonia that I've seen before include "Southernmost region of S America" , "part of South America" , "Region of South America" , "South American region" , "Craggy region" .)