Very hot substance in fatal avalanche (4)

I believe the answer is:

lava

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'very hot substance' is the definition.
'lava' can be an answer for 'substance' (lava is a kind of substance). I'm not certain of the 'very hot' bit.

'in fatal avalanche' is the wordplay.
'in' says the answer is hidden in the clue.
'LAVA' can be found hidden inside 'fatal avalanche'.

Can you help me to learn more?

(Other definitions for lava that I've seen before include "Hot flowing rock" , "Molten rock from volcanoes" , "Outflow from volcano" , "Volcanic emanation" , "It flows from volcano" .)

I've seen this clue in The Daily Express.

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