The most common and most likely answer to this crossword clue is the 8 letter word WHOPPING
I've seen this crossword clue in The Daily Telegraph
W
H
O
P
P
I
N
G
More clues leading to the result WHOPPING
Buddy explains!

The straight part
We know that "Very large" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case very large = whopping.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 WHOPPING mean?
WHOPPING verb- To throw or move (something) quickly, usually with an impact.
- To administer corporal punishment
- A beating.
- Exceptionally great or large.
- Exceedingly, extremely, very.