Beginning of rumblings in Mexico, the ground giving off heat (10)

I believe the answer is:

exothermic

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'beginning of rumblings in mexico the ground giving off heat' is the definition.
I can't judge whether this defines the answer.

'beginning of rumblings in mexico the ground' is the wordplay.
'beginning of' suggests taking the first letters.
'in' indicates putting letters inside.
'ground' is an anagram indicator ('grind' the letters into a new form).
The first letter of 'rumblings' is 'r'.
'mexico'+'the'='mexicothe'
'mexicothe' is an anagram of 'exothemic'.
'r' going inside 'exothemic' is 'EXOTHERMIC'.

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I've seen this clue in The Guardian.

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