Fathers rant about flag. (8)

I believe the answer is:

standard

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'flag' is the definition.
(I know that flag can be written as standard)

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for standard that I've seen before include "Level of quality; flag" , "Stock - basic - flag" , "Against which to measure the rest" , "Ordinary Level?" , "Flag - accepted level" .)

I've seen this clue in The Irish Times.

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