A lemon is an ingredient in making pasta (8)
I believe the answer is:
semolina
'making pasta' is the definition.
The definition and answer can be both things that one consumes for nourishment as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'a lemon is an ingredient' is the wordplay.
'an' becomes 'a'.
'ingredient' is an anagram indicator (I've seen 'ingredients' mean this).
'lemon'+'is'+'a'='lemonisa'
'lemonisa' is an anagram of 'SEMOLINA'.
'in' is the link.
Can you help me to learn more?
(Other definitions for semolina that I've seen before include "Form of wheat for puddings" , "Wheat powder" , "Milled wheat product" , "As oilmen eat this pudding" , "A lemon is used in the pudding, strangely" .)