Milan opera house (2,5)
'milan opera house' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for la scala that I've seen before include "Milanese opera house" , "A Callas seen in famous Milan opera house" , "noted venue?" , "music centre" , "place to sing" .)
(Other definitions for lascala that I've seen before include "theatre" , "music venue" .)