Crossword Genius

Critic and I regrettably offering caustic stuff (6,4)

Ross

I believe the answer is:

nitric acid

I'm a little stuck... Click here to teach me more about this clue!

'caustic stuff' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Maybe they are linked in a way I don't understand?

'critic and i regrettably' is the wordplay.
'regrettably' indicates anagramming the letters.
'critic'+'and'+'i'='criticandi'
'criticandi' anagrammed gives 'NITRIC ACID'.

'offering' is the link.

Can you help me to learn more?

(Other definitions for nitric acid that I've seen before include "Corrosive liquid" , "dangerous stuff?" , "component of explosive" .)

I've seen this clue in The Everyman puzzle in The Observer.
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