It may, of course, be suitable for tots (6)
I believe the answer is:
liquor
This clue could be a double definition.
'it may of course' is the first definition.
The definition suggests a singular noun which matches the answer.
'be suitable for tots' is the second definition.
The answer and definition can be both substances as well as being singular nouns.
Maybe there's a link between them I don't understand?
Can you help me to learn more?
(Other definitions for liquor that I've seen before include "Any alcholic drink" , "Alcoholic drink, booze" , "Alcoholic spirits" , "Alcoholic drink in general" , "Strong alcoholic drink" .)