The most common and most likely answer to this crossword clue is the 7 plus 3 letter word ODD-JOB MAN
O
D
D
-
J
O
B
M
A
N
Buddy explains!
The straight part
We know that "Casual worker" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case casual worker = odd-job man.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.