Fail to accept South American neglect (6)
I believe the answer is:
disuse
'neglect' is the definition.
(I've seen this before)
'fail to accept south american' is the wordplay.
'fail' becomes 'die' (synonyms).
'to accept' is an insertion indicator.
'south american' becomes 'sus' (I've seen this in other clues).
'die' enclosing 'sus' is 'DISUSE'.
(Other definitions for disuse that I've seen before include "Issued (anag)" , "Fall into this state to be unemplyed? (6)." , "Neglect; desuetude" , "State of not being employed" , "Neglect; abandonment" .)