The most common and most likely answer to this crossword clue is the 4 plus 5 letter word LOOM LARGE
I've seen this crossword clue in The Times
L
O
O
M
L
A
R
G
E
Buddy explains!
The straight part
We know that "to appear important" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case to appear important = loom large.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.