Prod weakling, one out in white bloomers (8)

I believe the answer is:

pokeweed

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'one out in white bloomers' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

'prod weakling' is the wordplay.
'prod' becomes 'poke' (synonyms).
'weakling' becomes 'weed' (I can't explain this - if you can you should believe this answer much more).
'poke'+'weed'='POKEWEED'

Can you help me to learn more?

I've seen this clue in The Independent.

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