The most common and most likely answer to this crossword clue is the 9 letter word REDEVELOP
I've seen this crossword clue in The Daily Telegraph
R
E
D
E
V
E
L
O
P
More clues leading to the result REDEVELOP
Buddy explains!

The straight part
We know that "Update" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case update = redevelop.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 REDEVELOP mean?
REDEVELOP verb- To develop again or differently.
- To intensify by a second process.
- To convert a neighbourhood by demolishing old buildings and building new ones, or by renovating existing ones.