Leicester bug, etc come from the salad vegetables (7,8)

I believe the answer is:

iceberg lettuces

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'vegetables' is the definition.
(iceberg lettuce is a kind of vegetable)

'leicester bug etc come from the salad' is the wordplay.
'leicester bug etc' can be anagrammed to 'ICEBERG LETTUCES'.
But, I'm not clear how this is indicated.

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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