The most common and most likely answer to this crossword clue is the 7 plus 6 letter word PASSING MUSTER
P
A
S
S
I
N
G
M
U
S
T
E
R
More clues leading to the result PASSING MUSTER
Buddy explains!

The straight part
We know that "make the grade" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case make the grade = passing muster.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.