Drink regularly in the bar (3)
I believe the answer is:
tea
'drink' is the definition.
(tea is a kind of drink)
'regularly in the bar' is the wordplay.
'regularly in' means one should take alternating letters.
'the'+'bar'='thebar'
The alternate letters of 'thebar' are 'TEA'.
(Other definitions for tea that I've seen before include "Popular beverage brewed at home" , "grass" , "Plantation product" , "bush" , "Afternoon meal (3)" .)