The most common and most likely answer to this crossword clue is the 10 letter word SLEEPYHEAD
I've seen this crossword clue in The Times
S
L
E
E
P
Y
H
E
A
D
More clues leading to the result SLEEPYHEAD
- In Peel's day he mistreated a dozy kid?
- Dozy type intelligence chief encountered outside shelter
- Artful teacher claims English exercises set back someone not attending fully?
- Inattentive person in shelter arrested by agent with brain
- He may be in danger of crashing
- 12 sheep delay broadcast
- Slacker ground he’d ply with ease
- One not totally alert, boss about to retire?
- He’s a deeply disturbed person wanting his bed
- When disturbed, she yelped — a dozy individual
Buddy explains!

The straight part
We know that "a dozy kid" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a dozy kid = sleepyhead.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 SLEEPYHEAD mean?
SLEEPYHEAD noun- A sleepy person.
- The ruddy duck.