The most common and most likely answer to this crossword clue is the 10 plus 5 letter word TWELVE-BAR BLUES
I've seen this crossword clue in The Guardian
T
W
E
L
V
E
-
B
A
R
B
L
U
E
S
Buddy explains!
The straight part
We know that "Music/depression after pub crawl" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case music/depression after pub crawl = twelve-bar blues.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.