The most common and most likely answer to this crossword clue is the 4 plus 2 plus 7 letter word LORD OF MISRULE
I've seen this crossword clue in The Times
L
O
R
D
O
F
M
I
S
R
U
L
E
Buddy explains!
The straight part
We know that "master of revelry" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case master of revelry = lord of misrule.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.