Turning dark and damp around South American region (7)
I believe the answer is:
midwest
'american region' is the definition.
(I've seen this before)
'turning dark and damp around south' is the wordplay.
'turning dark' becomes 'mid' (I can't justify this - if you can you should give a lot more credence to this answer).
'and' is a charade indicator (letters next to each other).
'damp' becomes 'wet' (similar in meaning).
'around' is an insertion indicator.
'south' becomes 'S' (abbreviation).
'wet' going around 's' is 'west'.
'mid'+'west'='MIDWEST'
Can you help me to learn more?
(Other definitions for midwest that I've seen before include "American region" , "Area from Ohio to the Rockies" , "North central region of the United States" , "US region" , "Central part of US" .)