The most common and most likely answer to this crossword clue is the 7 letter word LABARUM
L
A
B
A
R
U
M
Buddy explains!
The straight part
We know that "Moral guide" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case moral guide = labarum.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.
What does LABARUM mean?
LABARUM noun- The Roman military standard adopted by Constantine I. The banner was known for its Christian chi-rho sign - ☧.