The most common and most likely answer to this crossword clue is the 9 letter word SIMPERING
S
I
M
P
E
R
I
N
G
Buddy explains!
The straight part
We know that "Silly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case silly = simpering.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 SIMPERING mean?
SIMPERING verb- To smile in a foolish, frivolous, self-conscious, coy, or smug manner.
- To glimmer; to twinkle.
- The act of one who simpers.
- Smug, affected, and supercilious.