The most common and most likely answer to this crossword clue is the 7 letter word DOODLED
I've seen this crossword clue in The Guardian
D
O
O
D
L
E
D
More clues leading to the result DOODLED
Buddy explains!

The straight part
We know that "Sketched" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sketched = doodled.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 DOODLED mean?
DOODLED verb- To draw or scribble aimlessly.
- To drone like a bagpipe.