Taking issue over when work's done? (8-3,4)

I believe the answer is:

knocking-off time

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'work's done?' is the definition.
I know nothing about this answer so I cannot judge whether this works.

'taking issue over' is the wordplay.
'taking' becomes 'knocking off' (knocking off is a kind of taking).
'issue over' becomes 'time' (I am not sure about this - if you are sure you should believe this answer much more).
'knockingoff'+'time'='KNOCKING-OFF TIME'

'when' is the link.

Can you help me to learn more?

I've seen this clue in The Telegraph.

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