The most common and most likely answer to this crossword clue is the 3 plus 7 letter word TWO FINGERS
I've seen this crossword clue in The Guardian
T
W
O
F
I
N
G
E
R
S
More clues leading to the result TWO FINGERS
Buddy explains!
The straight part
We know that "V-sign /V-sign" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case v-sign /v-sign = two fingers.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.