The most common and most likely answer to this crossword clue is the 6 letter word SACKED
I've seen this crossword clue in Independent
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Buddy explains!

The straight part
We know that "dismissed" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dismissed = sacked.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 SACKED mean?
SACKED verb- (games) To sacrifice.
- To put in a sack or sacks.
- To bear or carry in a sack upon the back or the shoulders.
- To plunder or pillage, especially after capture; to obtain spoils of war from.
- To tackle the quarterback behind the line of scrimmage, especially before he is able to throw a pass.
- To discharge from a job or position; to fire.
- In the phrase sack out, to fall asleep. See also hit the sack.