Agrees law needs modifying to show true value of packet (4,5)

I believe the answer is:

real wages

'true value of packet' is the definition.

'agrees law needs modifying' is the wordplay.
'needs modifying' is an anagram indicator.
'agrees'+'law'='agreeslaw'
'agreeslaw' anagrammed gives 'REAL WAGES'.

'to show' is the link.

I've seen this clue in The Guardian.

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