Idiot putting drink on card (7)

I believe the answer is:

halfwit

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'idiot' is the definition.
(both can mean a stupid person)

'drink on card' is the wordplay.
'drink on' becomes 'half' (I've seen this before. I am not sure about the 'on' bit.).
'card' becomes 'wit' (synonyms).
'half'+'wit'='HALFWIT'

'putting' acts as a link.

Can you help me to learn more?

(Other definitions for halfwit that I've seen before include "dunce?" , "Idiot" , "Being stupid" , "Charlie?" , "One only 50% all there?" .)

I've seen this clue in The Telegraph.

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