Liars with witness strained relations (7,2,3)

I believe the answer is:

sisters in law

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

'liars with witness strained' is the wordplay.
'with' says to put letters next to each other.
'strained' indicates anagramming the letters.
'liars'+'witness'='liarswitness'
'liarswitness' with letters rearranged gives 'SISTERS-IN-LAW'.

(Another definition for sisters in law that I've seen is " Relations".)

I've seen this clue in The Times.

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