Girl that is following South American (5)
I believe the answer is:
susie
'girl' is the definition.
'that is following south american' is the wordplay.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'following' means one lot of letters go next to another.
'south' becomes 's' (abbreviation).
'american' becomes 'US' (United States).
's'+'us'='sus'
'ie' put after 'sus' is 'SUSIE'.
(Other definitions for susie that I've seen before include "Girl" , "Woman" , "Girl's name" , "Little Susannah" , "Tongue-twister sister sewing shirts for soldiers" .)