Hackneyed phrase heard in Hackney, falsely promising truth (3,4,2,5)

I believe the answer is:

its grim up north

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'hackneyed phrase heard in hackney' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'falsely promising truth' is the wordplay.
'falsely' indicates anagramming the letters.
'promising'+'truth'='promisingtruth'
'promisingtruth' is an anagram of 'ITS GRIM UP NORTH'.

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