Relating to La Serenissima (8)
I believe the answer is:
venetian
'relating to la serenissima' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for venetian that I've seen before include "Polo, say" , "Relating to La Serenissima" , "Blinds from an Italian city" , "-- blind; -- red; -- window" , "Like gondolas and blinds, say" .)