The most common and most likely answer to this crossword clue is the 6 letter word EJECTA
I've seen this crossword clue in Independent
E
J
E
C
T
A
More clues leading to the result EJECTA
- Etna’s insides become black, containing cold material thrown out
- Stuff thrown out in jamboree’s outside getting picked up by city volunteers
- Dismiss article — this issue’s volcanic
- It’s thrown out of eastern plane, one with cargo of cocaine
- Stuff thrown out, disheartening Jane, collected by city volunteers
Buddy explains!

The straight part
We know that "material thrown out" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case material thrown out = ejecta.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 EJECTA mean?
EJECTA noun- Material which has been ejected, especially from a volcano or an impact crater.