One of those in Rialto ain't even working (8)
I believe the answer is:
Here is my best explanation:
'one of those in rialto' is the definition.
I can't judge whether this defines the answer.
'ain't even working' is the subsidiary indication.
'working' is an anagram indicator.
'ainteven' is an anagram of 'venetian'.
(Other definitions for venetian that I've seen before include "Native like Marco Polo", "Relating to La Serenissima", "Blinds from an Italian city", "Citizen of Italy's water city", "Of a city of canals", "One like Marco Polo", "-- blind; -- red; -- window", "Type of Italian", "Like gondolas and blinds, say" and "Polo, say".)