Emaciated family in South American city (6)
I believe the answer is:
skinny
'emaciated' is the definition.
(I've seen this before)
'family in south american city' is the wordplay.
'family' becomes 'kin' (synonyms).
'in' means one lot of letters goes inside another.
'south' becomes 's' (abbreviation).
'american city' becomes 'ny' (short for New York).
's'+'ny'='sny'
'kin' placed within 'sny' is 'SKINNY'.
(Other definitions for skinny that I've seen before include "Not very well-built" , "Unattractively thin" , "not having much in the way of meat" , "Euphemism for a caffe latte with skimmed (non-fat) milk" , "Scrawny, underweight" .)