Shallow vessel containing little drop (8)
I believe the answer is:
diminish
'drop' is the definition.
(I've seen this before)
'shallow vessel containing little' is the wordplay.
'shallow vessel' becomes 'dish' (I can't explain this - if you can you should give a lot more credence to this answer).
'containing' is an insertion indicator.
'little' becomes 'mini'.
'dish' enclosing 'mini' is 'DIMINISH'.
Can you help me to learn more?
(Other definitions for diminish that I've seen before include "Make or become smaller" , "Drop" , "Make less with mini dish" , "Contract" , "get shorter" .)