The most common and most likely answer to this crossword clue is the 4 plus 4 plus 5 letter word WEST SIDE STORY
I've seen this crossword clue in Financial Times
W
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More clues leading to the result WEST SIDE STORY
- Direction borders on conservative in Romeo and Juliet adaptation
- Musical sister’s to wed oddball before start of year
- Sets off in very spacious gold yacht to start production
- Show managed its seedy worst
- Musical districts on the left and on the right?
- Show Conservative support for May’s broadcast on the 15th?
- Extra floor said to accommodate new sets for musical
- Show direction on pages followed by Conservative
Buddy explains!

The straight part
We know that "musical" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case musical = west side story.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.