Tin containing new filling: potato and cabbage (9)
I believe the answer is:
colcannon
'cabbage' is the definition.
Both the answer and definition are singular nouns.
Maybe you can see an association between them that I can't see?
'tin containing new filling potato' is the wordplay.
'tin' becomes 'can' (synonyms).
'containing' means one lot of letters goes inside another.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'filling' is an insertion indicator.
'potato' becomes 'colon' (I can't explain this - if you can you should believe this answer much more).
'can' enclosing 'n' is 'cann'.
'cann' placed inside 'colon' is 'COLCANNON'.
'and' is the link.
Can you help me to learn more?
(Other definitions for colcannon that I've seen before include "fed to the Irish?" , "Vegetarian dish for 19 [PADRAIC]" , "Food for Irish" , "plate for Seamus?" , "Traditional Irish dish of mashed potatoes and cabbage" .)