Volume company supports, including article that’s hot stuff in it? (7)
I believe the answer is:
volcano
'hot stuff in it?' is the definition.
(volcanos contain magma)
'volume company supports including article' is the wordplay.
'volume' becomes 'vol'.
'company' becomes 'co' (abbreviation).
'supports' is a charade indicator (letters next to each other) (bottom letters provide a support for the top ones).
'including' is an insertion indicator.
'article' becomes 'an' (English indefinite article).
'vol'+'co'='volco'
'volco' going around 'an' is 'VOLCANO'.
'that's' acts as a link.
(Other definitions for volcano that I've seen before include "One expelling lava etc." , "Dangerous mountain like Stromboli or Etna" , "kind of mountain" , "Eg, Eyjafjallajokull" , "Erupting hole in the earth's crust" .)