The most common and most likely answer to this crossword clue is the 12 plus 1 plus 3 letter word UNAPOLOGETIC - UNA
I've seen this crossword clue in The Times
U
N
A
P
O
L
O
G
E
T
I
C
-
U
N
A
Buddy explains!
The straight part
We know that "making no excuses" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case making no excuses = unapologetic - una.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.