The most common and most likely answer to this crossword clue is the 7 plus 7 letter word RICHARD STRAUSS
I've seen this crossword clue in The Guardian
R
I
C
H
A
R
D
S
T
R
A
U
S
S
More clues leading to the result RICHARD STRAUSS
Buddy explains!
The straight part
We know that "musician" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case musician = richard strauss.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.