We'll need this one as pot boils! (8)
I believe the answer is:
teaspoon
'we'll need this one as pot boils' is the definition.
The definition and answer can be both quantities as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'one as pot boils' is the wordplay.
'boils' is an anagram indicator (I've seen 'boiling' mean this).
'one'+'as'+'pot'='oneaspot'
'oneaspot' with letters rearranged gives 'TEASPOON'.
Can you help me to learn more?
(Other definitions for teaspoon that I've seen before include "Five millilitres (cookery)" , "Cooking unit" , "Small medicine dispensing unit" , "Small piece of cutlery" , "Small item of cutlery (8)" .)