The most common and most likely answer to this crossword clue is the 5 letter word PAVES
I've seen this crossword clue in The Guardian
P
A
V
E
S
More clues leading to the result PAVES
Buddy explains!
The straight part
We know that "flags" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case flags = paves.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 PAVES mean?
PAVES verb- To cover something with paving slabs.
- To cover with stone, concrete, blacktop or other solid covering, especially to aid travel.
- To pave the way for; to make easy and smooth.