Having departed from the house for good, was a blow (4,4)

'good was a blow' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'having departed from the house' is the wordplay.
I cannot really understand how this works, but
'departed' could be 'left' (to leave is to depart) and 'left' is found in the answer.
'from' could be 'o' (I've seen this in other clues) and 'o' is found in the answer.
'house' could be 'ho' (abbreviation for house) and 'ho' is found in the answer.
A single letter 'k' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

'for' is the link.

Can you help me to learn more?