The most common and most likely answer to this crossword clue is the 3 plus 2 plus 5 letter word NOT AT ISSUE
N
O
T
A
T
I
S
S
U
E
Buddy explains!
The straight part
We know that "Missing from agenda" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case missing from agenda = not at issue.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.