Faulty oil and gas lines between corners (9)

I believe the answer is:

diagonals

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'lines between corners' is the definition.
I can't judge whether this defines the answer.

'faulty oil and gas' is the wordplay.
'faulty' is an anagram indicator.
'oil'+'and'+'gas'='oilandgas'
'oilandgas' anagrammed gives 'DIAGONALS'.

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I've seen this clue in the Sydney Morning Herald.

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