Piano in old time musical drama (5)
I believe the answer is:
opera
'musical drama' is the definition.
(I've seen this before)
'piano in old time' is the wordplay.
'piano' becomes 'p' (musical abbreviation).
'in' is an insertion indicator.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'time' becomes 'era' (era is a kind of time).
'o'+'era'='oera'
'p' going into 'oera' is 'OPERA'.
(Other definitions for opera that I've seen before include "Eg, Der Rosenkavalier" , "Aida, for example" , "E.g. Macbeth, Falstaff" , "Stage entertainment" , "La Scala production, perhaps" .)