Venetian landmark (6,2,5)
I believe the answer is:
bridge of sighs
'venetian landmark' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for bridge of sighs that I've seen before include "Venetian attraction" , "Venetian construction across which prisoners were once led to trial" , "Venetian landmark" , "Prison passage" , "Venice tourist attraction" .)