The most common and most likely answer to this crossword clue is the 3 plus 10 letter word LES MISERABLES
I've seen this crossword clue in The Daily Telegraph
L
E
S
M
I
S
E
R
A
B
L
E
S
More clues leading to the result LES MISERABLES
- Dancing bears seem ill prepared at beginning of scene in musical
- Sees Monsieur bear ills in performance of this?
- Novel end for festival with electronic beams wrapping displays up
- Say, Fagin and Artful appearing in not so successful musical
- Novel in which the blameless rise in rebellion
- Liberals seem upset by society’s work on injustice
Buddy explains!
The straight part
We know that "successful musical" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case successful musical = les miserables.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.