The most common and most likely answer to this crossword clue is the 2 plus 4 letter word NO MORE
I've seen this crossword clue in The Sunday Telegraph
N
O
M
O
R
E
More clues leading to the result NO MORE
- New moon about to be late
- Passed on some revolting pheromones
- In time computer memory is flipping dead
- A thousand in African country abandoning river on the rise, departed
- What’s in name? Romeo tragically passed away
- Drama with extinct bird, mostly about having ceased to be
- Dead equal or fewer?
- Moron edited first edition — never again!
- Exhausted — never again!
- Gold in Alaskan city? Not now
Buddy explains!

The straight part
We know that "Dead" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dead = no more.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.