The most common and most likely answer to this crossword clue is the 7 letter word IGNEOUS
I've seen this crossword clue in The Times
I
G
N
E
O
U
S
More clues leading to the result IGNEOUS
- Like granite or wooden surface scrubbed
- Go in and use rocks like volcanic rock
- Kind of rock wayward genius has put in ring
- Rock type mad genius found round rear of volcano
- Fiery gas insufficient to stop inauguration of Imperator Augustus
- Sort of rock group: it’s one not electrified, since unplugging leads surprisingly
- As some rocks are eg in jerry-built house without walls
- Fiery genius collapsed outside ring
- Like some rock genius confused about love?
- Like some rock, i.e. song played around university
Buddy explains!
The straight part
We know that "Kind of rock" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case kind of rock = igneous.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 IGNEOUS mean?
IGNEOUS adjective- Pertaining to or having the nature of fire; containing fire; resembling fire.
- Resulting from, or produced by, great heat. With rocks, it could also mean formed from lava or magma.