Show with established soprano that is gold - the ultimate in Broadway (4,4,5)
I believe the answer is:
west side story
'show' is the definition.
(I've seen this before)
'established soprano that is gold the ultimate in broadway' is the wordplay.
'established soprano' becomes 'wests' (I can't explain this - if you can you should believe this answer much more).
'that is' becomes 'id est' ('that is' in Latin).
'gold' becomes 'or' ('or' is the heraldic name for gold).
'the ultimate in' says to take the final letters.
The last letter of 'broadway' is 'y'.
'wests'+'idest'+'or'+'y'='WEST SIDE STORY'
'with' acts as a link.
(Other definitions for west side story that I've seen before include "Romeo and Juliet adaptation" , "1961 film based on Romeo and Juliet, set in a New York slum" , "New-York-gangs musical" , "1957 musical set in New York City" , "Well-known musical" .)