The most common and most likely answer to this crossword clue is the 5 plus 8 letter word BILLY NO-MATES
B
I
L
L
Y
N
O
-
M
A
T
E
S
Buddy explains!
The straight part
We know that "being without friends" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case being without friends = billy no-mates.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.