Corrosive liquid (4)
I believe the answer is:
acid
'corrosive liquid' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for acid that I've seen before include "Caustic and biting" , "Sour, sharp-tasting" , "Sarcastic - tart" , "Battery fluid" , "Hallucinogenic drug" .)