Critic and I mixed caustic liquid (6,4)
I believe the answer is:
nitric acid
'caustic liquid' is the definition.
'nitric acid' can be an answer for 'liquid' (I have seen 'Corrosive liquid ' mean 'nitric acid' so perhaps 'liquid' could also mean 'nitric acid'). I'm unsure of the 'caustic' bit.
'critic and i mixed' is the wordplay.
'mixed' indicates anagramming the letters.
'critic'+'and'+'i'='criticandi'
'criticandi' anagrammed gives 'NITRIC ACID'.
Can you help me to learn more?
(Other definitions for nitric acid that I've seen before include "dangerous stuff?" , "Corrosive liquid" , "component of explosive" .)