The most common and most likely answer to this crossword clue is the 5 letter word FLUNG
I've seen this crossword clue in The Daily Telegraph
F
L
U
N
G
More clues leading to the result FLUNG
Buddy explains!

The straight part
We know that "Cast" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cast = flung.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 FLUNG mean?
FLUNG verb- To move (oneself) abruptly or violently; to rush or dash.
- To throw with violence or quick movement; to hurl.
- To throw; to wince; to flounce.
- To utter abusive language; to sneer.