Supplier of spam left in snack? I'm not sure (7)

I believe the answer is:

flooder

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'supplier of spam left in snack? i'm not sure' is the definition.
I can't tell whether this definition defines the answer.

'left in snack? i'm not sure' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in' indicates putting letters inside.
'snack?' becomes 'food' (snack is a kind of food).
'i'm not sure' becomes 'er' (expression of hesitation).
'l' inserted inside 'food' is 'flood'.
'flood'+'er'='FLOODER'

Can you help me to learn more?

I've seen this clue in The Independent.

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