South American chain oddly ignored food (5)
I believe the answer is:
sushi
'food' is the definition.
(sushi is a kind of food)
'south american chain oddly ignored' is the wordplay.
'south american' becomes 'sus' (I've seen this in other clues).
'oddly ignored' indicates alternate letters.
The alternating letters of 'chain' are 'hi'.
'sus'+'hi'='SUSHI'
(Other definitions for sushi that I've seen before include "Oriental food" , "Japanese cold rice dish" , "Japanese rice-based dish" , "Asian food" , "Cold rice dish, often with raw fish" .)