Non-vegetarian food the old king left (5)

I believe the answer is:

offal

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'non-vegetarian food' is the definition.
I can't judge whether this defines the answer.

'old king left' is the wordplay.
'old king' becomes 'offa' (King of Mercia).
'left' becomes 'l' (common abbreviation).
'offa'+'l'='OFFAL'

'the' is the link.

Can you help me to learn more?

(Other definitions for offal that I've seen before include "Liver, lungs etc" , "Heart, liver, kidney etc" , "Butcher's leftovers" , "Internal organs of an animal some find tasty" , "Waste parts of a carcass" .)

I've seen this clue in the Evening Standard.

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