The most common and most likely answer to this crossword clue is the 4 plus 2 plus 3 plus 5 letter word LORD OF THE ISLES
I've seen this crossword clue in Financial Times
L
O
R
D
O
F
T
H
E
I
S
L
E
S
Buddy explains!
The straight part
We know that "Prince Charles" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case prince charles = lord of the isles.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.