Partly open a drink (4)

I believe the answer is:

ajar

'partly open' is the definition.
(as in a door which has been left ajar)

'a drink' is the wordplay.
'drink' becomes 'jar' (colloquial).
'a'+'jar'='AJAR'

(Other definitions for ajar that I've seen before include "partly opened" , "Not quite closed" , "Half open" , "near closing?" , "Mourn" .)

I've seen this clue in The Telegraph.

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