Brew beer, only half jug (4)

I believe the answer is:

ewer

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'jug' is the definition.
(type of vessel)

'brew beer only half' is the wordplay.
'brew' becomes 'ew' (I can't justify this - if you can you should believe this answer much more).
'only half' indicates taking half.
'beer' with half the letters taken is 'er'.
'ew'+'er'='EWER'

Can you help me to learn more?

(Other definitions for ewer that I've seen before include "A wide-lipped jug" , "Jar for water" , "Oversized jug" , "Large pitcher" , "water-carrier" .)

I've seen this clue in The Guardian.

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