Crate containing small part needed for pot (9)
I believe the answer is:
casserole
'for pot' is the definition.
(type of cooking pot)
'crate containing small part' is the wordplay.
I cannot quite understand how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is found within the answer.
'part' could be 'role' (eg a theatrical role) and 'role' is present in the answer.
The remaining letters 'case' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'needed' is the link.
(Other definitions for casserole that I've seen before include "Oven dish" , "Slow-cooked dish" , "meal" , "So cereals may be used for this oven-cooked covered dish" , "(Food cooked in a) stewpot" .)