Eruption results in some upheaval back there (4)
I believe the answer is:
lava
'eruption' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'results in some upheaval back there' is the wordplay.
'results in' is an anagram indicator (I've seen 'resulting in' mean this).
'some' becomes 'a'.
'back' suggests the final letters.
'there' becomes 'va' (I can't explain this - if you can you should believe this answer much more).
The last letter of 'upheaval' is 'l'.
'a'+'l'='al'
'al' with letters rearranged gives 'la'.
'la'+'va'='LAVA'
Can you help me to learn more?
(Other definitions for lava that I've seen before include "It flows from volcano" , "Volcanic emanation" , "Volcanic outpouring" , "Molten volcanic rock" , "Molten volcanic material" .)