See, in plaza, endless filth (7)
I believe the answer is:
squalor
'filth' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for squalor that I've seen before include "Dirt and untidiness" , "Sleaziness, mean poverty" , "Extremely dirty state" , "Dirty conditions" , "State of misery and filth" .)