They're highly regarded in South America (5)
I believe the answer is:
andes
'in south america' is the definition.
('Andes' is part of 'south america')
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for andes that I've seen before include "South American mountain range" , "Great S American mountains" , "South American mountain chain" , "A geographical feature" , "The range of llamas?" .)