Crossword Genius

An infringement of what marks the boundary (7)

Ross

I believe the answer is:

offence

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'an infringement' is the definition.
(synonyms)

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(Other definitions for offence that I've seen before include "Displeasure" , "Violation" , "Hurt; military attack" , "Misdeed" , "Criminal action" .)

I've seen this clue in The Irish Independent.
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