Invention of a cold snack (7)

I believe the answer is:

porkpie

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'invention' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?

'cold snack' is the wordplay.
'cold' becomes 'pork' (I am not sure about this - if you are sure you should believe this answer much more).
'snack' becomes 'pie'.
'pork'+'pie'='PORKPIE'

'of a' acts as a link.

Can you help me to learn more?

I've seen this clue in The Times.

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