Rail in pub (3)
I believe the answer is:
bar
I believe this is a double definition.
'rail' is the first definition.
(thesaurus)
'pub' is the second definition.
(I've seen this before)
'in' acts as a link.
(Other definitions for bar that I've seen before include "In Mississippi, measure" , "Save; pub" , "See 9" , "Drinking place - lawyers!" , "Saloon" .)