Outlaw goat and its offspring (5,3,3)

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

'goat and its offspring' is the wordplay.
'goat' becomes 'billy goat' (billy goat is a kind of goat).
'and' is a charade indicator (letters next to each other).
'its' becomes 'the' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'offspring' becomes 'kid' (kid is a kind of offspring).
'billy'+'the'+'kid'='BILLY THE KID'