Second Avenue rescue (4)
I believe the answer is:
save
'rescue' is the definition.
(I know that rescue is a more specific form of the action save)
'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 from danger" , "Hang on to" , "Rescue - except" , "Rescue and put money aside" , "Except; hoard" .)