Warning that comes with a new coat (3,5)
I believe the answer is:
wet paint
'warning that comes' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'a new coat' is the wordplay.
'a new' becomes 'wet' (I can't explain this - if you can you should believe this answer much more).
'coat' becomes 'paint' (painting is a kind of coating).
'wet'+'paint'='WET PAINT'
'with' is the link.
Can you help me to learn more?
(Other definitions for wet paint that I've seen before include "A fresh coat - twin tape (anag)" , "Post-decorating notice" .)