The most common and most likely answer to this crossword clue is the 6 letter word PENNON
I've seen this crossword clue in The Daily Telegraph
P
E
N
N
O
N
More clues leading to the result PENNON
- Continue writing about northern flag
- Standard sports news being shown
- Keep writing about new standard
- Write name before getting aboard, standard for ship
- Ivy League university, one briefly showing flag
- Pressure on singers to hold new nationalist flag
- State University on flag
- University atop flag
- Flag poles positioned in time to follow president
- Write name on flag
Buddy explains!

The straight part
We know that "flag" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case flag = pennon.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PENNON mean?
PENNON noun- A thin, often triangular flag or streamer, especially as hung from the end of a lance or spear.
- A long pointed streamer or flag on a vessel.
- A wing (appendage of an animal's body enabling it to fly); any of the outermost primary feathers on a wing.