Feeling tension developing around South America (9)
I believe the answer is:
sensation
'feeling' is the definition.
(sensation is a kind of feeling)
'tension developing around south america' is the wordplay.
'developing' indicates an anagram.
'around' indicates putting letters inside.
'south' becomes 's' ('S' can be a synonym of 'south').
'america' becomes 'a' (common abbreviation - e.g. in organisation names).
'tension' anagrammed gives 'sention'.
's'+'a'='sa'
'sention' placed around 'sa' is 'SENSATION'.
(Other definitions for sensation that I've seen before include "Scandal" , "Feeling produced by stimulation, or dramatic news (9)" , "Crowd puller" , "Feeling, awareness of stimulation" , "Physical feeling or perception" .)