How marcher's flag might be confirmed? (6)
I believe the answer is:
upheld
'confirmed?' is the definition.
(upholding is a kind of confirming)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for upheld that I've seen before include "Supported decision or belief" , "Sustained" , "Confirmed, supported" , "Confirmed something disputed" , "Maintained (a custom)" .)