The most common and most likely answer to this crossword clue is the 7 letter word URANIUM
I've seen this crossword clue in The Times
U
R
A
N
I
U
M
More clues leading to the result URANIUM
- Skull with front modified, something dangerously unstable
- A little unwisely, skull cap removed for heavy metal
- Element in uniform with skull cap removed?
- Element in place of education probed by artist with doubtful expression
- Metal content of mug or cup, perhaps?
- Posh auntie regularly in company of peculiar element
- Metal found in heart of crust
- Greek character in a game, rising element
- One’s written on table at school? A case for the head, given united front
- Element I’m not sure will support posh queen
Buddy explains!
The straight part
We know that "something dangerously unstable" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case something dangerously unstable = uranium.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 URANIUM mean?
URANIUM noun- The element with atomic number 92 and symbol U: a radioactive silvery-grey metal in the actinide series.