Lady true? Possibly not with this (8)

I believe the answer is:

adultery

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'not with this' is the definition.
The definition suggests a singular noun which matches the answer.

'lady true? possibly' is the wordplay.
'possibly' indicates anagramming the letters.
'lady'+'true'='ladytrue'
'ladytrue' anagrammed gives 'ADULTERY'.

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(Other definitions for adultery that I've seen before include "Unfaithfulness to one's spouse" , "The act of being unfaithful to spouse (8)" , "excluding union involvement?" , "Sexual unfaithfulness to spouse" , "cheating" .)

I've seen this clue in The Sun.

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