Ineffective agreement passed by landlord? (4,6)

I believe the answer is:

dead letter

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'landlord?' is the definition.
(I have seen 'Unresponsive landlord' mean 'dead letter' so perhaps 'landlord' could also mean 'dead letter')

I can't explain the remainder of the clue.

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(Other definitions for dead letter that I've seen before include "Itll not lead to prosecution" , "Unresponsive landlord" , "Ineffective rule" , "Law no longer enforced" , "no longer observed" .)

I've seen this clue in The Irish Times.

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