The most common and most likely answer to this crossword clue is the 5 letter word LIMED
I've seen this crossword clue in The Times
L
I
M
E
D
Buddy explains!

The straight part
We know that "Given some whitewash" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case given some whitewash = limed.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 LIMED mean?
LIMED verb- To treat with calcium hydroxide or calcium oxide (lime).
- To smear with birdlime.
- To apply limewash.
- To hang out/socialize in an informal, relaxed environment, especially with friends, for example at a party or on the beach.