Establishment purveying beer: diet? (5)
I believe the answer is:
local
This clue is a double definition.
'establishment purveying beer' is the first definition.
(term for a pub)
'diet?' is the second definition.
(lo-cal is short for 'low calories')
(Other definitions for local that I've seen before include "Convenient pub" , "In the vicinity" , "Nieghbourhood pub or its customer" , "belonging to particular area?" , "Pub down the road?" .)