A bad standard in the main (6,4)

I believe the answer is:

pirate flag

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'the main' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I don't see?

'a bad standard' is the wordplay.
'a bad' becomes 'pirate' (I can't explain this - if you can you should give a lot more credence to this answer).
'standard' becomes 'flag' (standard is a type of flag).
'pirate'+'flag'='PIRATE FLAG'

'in' is the link.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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