Second Avenue bar (4)
I believe the answer is:
save
'bar' is the definition.
(save is a kind of bar)
'second avenue' is the wordplay.
'second' becomes 's' (common abbreviation).
'avenue' becomes 'ave' (**).
's'+'ave'='SAVE'
(Other definitions for save that I've seen before include "Rescue - economise" , "Rescue from harm" , "deliver from evil" , "Rescue and put money aside" , "Prepare for a rainy day" .)