Drink popular between bridge partners (4)
I believe the answer is:
wine
'drink' is the definition.
(wining is a kind of drinking)
'popular between bridge partners' is the wordplay.
'popular' becomes 'in'.
'between' is an insertion indicator.
'bridge partners' becomes 'we' (West and East are players in the card game bridge).
'in' placed within 'we' is 'WINE'.
(Other definitions for wine that I've seen before include "Alcoholic grape juice" , "Plonk" , "See 18" , "Beaujolais, for example" , "champagne, perhaps" .)