Crossword Genius

Run out of caustic chemical (4)

Ross

I believe the answer is:

acid

'chemical' is the definition.
(thesaurus)

'run out of caustic' is the wordplay.
'run' becomes 'r' (cricket abbreviation).
'out of' is a deletion indicator.
'caustic' becomes 'acrid' (I've seen this before).
'acrid' with 'r' removed is 'ACID'.

(Other definitions for acid that I've seen before include "Drug LSD (colloq.)" , "Corrosive fluid" , "Sour - vitriolic" , "Corrosive liquid; drug" , "Bitter or sour" .)

I've seen this clue in The Independent.
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