Knockout stuff from loch or ground (10)

I believe the answer is:

chloroform

'knockout stuff' is the definition.

'from loch or ground' is the wordplay.
'ground' is an anagram indicator ('grind' the letters into a new form).
'from'+'loch'+'or'='fromlochor'
'fromlochor' with letters rearranged gives 'CHLOROFORM'.

(Other definitions for chloroform that I've seen before include "Old anaesthetic" , "Solvent" , "Former anaesthetic" , "Sweet-smelling anaesthetic" .)

I've seen this clue in The Guardian.

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