The most common and most likely answer to this crossword clue is the 9 letter word FIDGETING
F
I
D
G
E
T
I
N
G
Buddy explains!

The straight part
We know that "wriggling" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case wriggling = fidgeting.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 FIDGETING mean?
FIDGETING verb- To wiggle or twitch; to move around nervously or idly.
- To cause to fidget; to make uneasy.
- A fidgety motion.