Tip plain vessel which may have tea in it (8)
I believe the answer is:
overturn
'tip' is the definition.
(I've seen this before)
'plain vessel which may have tea in it' is the wordplay.
I cannot quite understand how this works, but
'plain' could be 'overt' (both can mean visible or obvious) and 'overt' is found within the answer.
'vessel' could be 'urn' (urn is a type of container) and 'urn' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for overturn that I've seen before include "Invert" , "tip" , "Crash" , "Revoke" , "Invalidate - upset" .)