The most common and most likely answer to this crossword clue is the 9 letter word IRRIGATED
I've seen this crossword clue in The Daily Telegraph
I
R
R
I
G
A
T
E
D
More clues leading to the result IRRIGATED
Buddy explains!

The straight part
We know that "Washed out" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case washed out = irrigated.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 IRRIGATED mean?
IRRIGATED verb- To supply (farmland) with water, by building ditches, pipes, etc.
- To clean (a wound) with a fluid.