Pub's popular name (3)
I believe the answer is:
inn
'pub's' is the definition.
(an inn is a type of pub)
'popular name' is the wordplay.
'popular' becomes 'in' ('in' can mean trendy).
'name' becomes 'n' (common abbreviation e.g. on forms).
'in'+'n'='INN'
(Other definitions for inn that I've seen before include "It provides rest for the traveller" , "Local" , "Hotel with lodging for travellers" , "One of Lincoln's" , "Swiss river" .)