The most common and most likely answer to this crossword clue is the 9 letter word OFFHANDED
I've seen this crossword clue in The Times
O
F
F
H
A
N
D
E
D
More clues leading to the result OFFHANDED
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The straight part
We know that "Casual" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case casual = offhanded.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 OFFHANDED mean?
OFFHANDED adjective- In a casual or curt style, without preparation or thought; Impromptu, offhand.