As a drudge mother I perform sink duty (4,2,3,4)

'as a drudge mother' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'i perform sink duty' is the wordplay.
I cannot quite see how this works, but
'i' could be 'a' and 'a' is located in the answer.
'perform' could be 'do' (both can mean complete an action) and 'do' is present in the answer.
'sink' could be 'fall' (I've seen this in another clue) and 'fall' is located in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?