Who can fill an empty beer jug? (6)
I believe the answer is:
brewer
'who can fill an empty beer jug?' is the definition.
I know that 'beer' relates to this answer.
'empty beer jug?' is the wordplay.
'empty' suggests removing the centre.
'jug?' becomes 'ewer' (type of vessel).
'beer' with its centre taken out is 'br'.
'br'+'ewer'='BREWER'
(Other definitions for brewer that I've seen before include "One makes beer" , "Tendency to seek perfection" , "Beer manufacturer" , "one needing teapot?" , "Beer (or tea?) maker" .)