The most common and most likely answer to this crossword clue is the 8 letter word RICHNESS
I've seen this crossword clue in The Guardian
R
I
C
H
N
E
S
S
Buddy explains!
The straight part
We know that "magnificence" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case magnificence = richness.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 RICHNESS mean?
RICHNESS noun- The state or quality of being rich; richdom; wealth.
- The state of having many examples or cases; abundance; profusion.
- The number of types in a community.
- The result or product of being rich.