Flags on the street (6,6)
I believe the answer is:
paving stones
'flags on the street' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Maybe they are linked in a way I don't understand?
'street' is the wordplay.
I cannot really see how this works, but
'street' could be 'st' (abbreviation) and 'st' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for paving stones that I've seen is " Concrete slabs for walking on".)