Cure a hill-dweller at four before baseball team returns (9)

'cure' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's an association between them I don't understand?

'a hill-dweller at four before baseball team returns' is the wordplay.
'a hill dweller' becomes 'ant' (I've seen this in another clue).
'at' means one lot of letters go next to another.
'four before' becomes 'iv' (I can't explain this - if you can you should give a lot more credence to this answer).
'baseball team' becomes 'nine' (synonyms).
'returns' says the letters should be written backwards.
'nine' back-to-front is 'enin'.
'ant'+'iv'+'enin'='ANTIVENIN'

Can you help me to learn more?