Waller starts to take on cattle, keeping animals for slaughter (8)

'animals for slaughter' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'waller starts to take on cattle' is the wordplay.
'waller' becomes 'fats' (I've seen this in another clue).
'starts' means to remove the last letter.
'to take on' means one lot of letters go next to another.
'cattle' becomes 'stock' (I've seen this before).
'fats' with its final letter removed is 'fat'.
'fat'+'stock'='FATSTOCK'

'keeping' is the link.

Can you help me to learn more?