Wine sent back when eating pub grub (6)
I believe the answer is:
dinner
'grub' is the definition.
(I've seen this before)
'wine sent back when eating pub' is the wordplay.
'wine' becomes 'red wine' (red is a type of wine).
'sent back' says the letters should be written in reverse.
'when eating' indicates putting letters inside.
'pub' becomes 'inn' (an inn is a type of pub).
'red' in reverse letter order is 'der'.
'der' going around 'inn' is 'DINNER'.
(Other definitions for dinner that I've seen before include "Supper" , "grub" , "Main meal of day" , "What feeds" , "one making a row?" .)