The most common and most likely answer to this crossword clue is the 8 letter word GESTURAL
I've seen this crossword clue in The Times
G
E
S
T
U
R
A
L
More clues leading to the result GESTURAL
Buddy explains!

The straight part
We know that "As hand waving" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case as hand waving = gestural.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.