Anti-labour act? (7)

I believe the answer is:

lockout

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'anti-labour act?' is the definition.
I can't judge whether this definition defines the answer.

'anti-labour act?' is the wordplay.
'anti-labour' becomes 'lock' (I can't explain this - if you can you should give a lot more credence to this answer).
'act?' becomes 'out' (out is a kind of act).
'lock'+'out'='LOCKOUT'

Can you help me to learn more?

(Other definitions for lockout that I've seen before include "Labour dispute" , "management action" .)

I've seen this clue in The Globe and Mail.

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