Force out an obsolete law (5)

I believe the answer is:

exact

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'force out' is the definition.
(I've seen this before)

'an obsolete law' is the wordplay.
'an obsolete' becomes 'ex' (I can't justify this - if you can you should give a lot more credence to this answer).
'law' becomes 'act' (I've seen this before).
'ex'+'act'='EXACT'

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(Other definitions for exact that I've seen before include "Completely accurate" , "dead" , "Spot on, precise" , "Precisely accurate" , "On the nail" .)

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

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