It holds liquid of course (4,5)
I believe the answer is:
soup plate
'it holds liquid' is the definition.
The definition suggests a singular noun which matches the answer.
'of course' is the wordplay.
'of' becomes 'soup' (I can't explain this - if you can you should believe this answer much more).
'course' becomes 'plate' (plate is a kind of course).
'soup'+'plate'='SOUP PLATE'
Can you help me to learn more?
(Other definitions for soup plate that I've seen before include "Item of crockery" , "Deep dish" , "Serving dish" .)