Seems, when mixing the drink, one bungles it (6,2)

I believe the answer is:

messes up

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'one bungles it' is the definition.
I can't judge whether this defines the answer.

'seems when mixing the drink' is the wordplay.
'when mixing' indicates anagramming the letters.
'the drink' becomes 'sup' (to sup is to drink).
'seems' with letters rearranged gives 'messe'.
'messe'+'sup'='MESSES UP'

Can you help me to learn more?

(Another definition for messes up that I've seen is " Mishandles a situation".)

I've seen this clue in the Evening Standard.

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