It emits lava (7)
I believe the answer is:
volcano
'it emits lava' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for volcano that I've seen before include "Lava-spewing mountain" , "St Helens?" , "Dangerous mountain like Stromboli or Etna" , "Fiery mountain" , "kind of mountain" .)