Half shut off leakage and get cracking (5,1,3)

I believe the answer is:

shake a leg

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'get cracking' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'half shut off leakage' is the wordplay.
'half' indicates taking half.
'off' is an anagram indicator.
'shut' cut in half is 'sh'.
'leakage' is an anagram of 'akealeg'.
'sh'+'akealeg'='SHAKE A LEG'

'and' acts as a link.

Can you help me to learn more?

(Other definitions for shake a leg that I've seen before include "Get up - be productive" , "Get a move on" , "Hurry up" .)

I've seen this clue in the Sydney Morning Herald.

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