Musical work taking a long time to produce (5)
I believe the answer is:
opera
'musical work' is the definition.
(I've seen this before)
'a long time to produce' is the wordplay.
'a long time' becomes 'era' (a long period of time).
'to' means one lot of letters go next to another (I've seen this in other clues).
'produce' becomes 'op' (I can't justify this - if you can you should believe this answer much more).
'era' after 'op' is 'OPERA'.
'taking' is the link.
Can you help me to learn more?
(Other definitions for opera that I've seen before include "10 [NORMA], for example" , "Stage entertainment" , "could be soap" , "Macbeth, perhaps" , "Norma is one" .)