Hot substance in fatal avalanche (4)

I believe the answer is:

lava

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'hot substance' is the definition.
'lava' can be an answer for 'substance' (lava is a kind of substance). I'm unsure of the 'hot' bit.

'in fatal avalanche' is the wordplay.
'in' indicates a hidden word.
'LAVA' is hidden in the letters of 'fatal avalanche'.

Can you help me to learn more?

(Other definitions for lava that I've seen before include "Molten matter from volcano" , "Flowing volcanic matter" , "Volcanic emanation" , "Volcano output" , "Stuff heatedly hurled out" .)

I've seen this clue in The Daily Express.

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