Help or benefit (5)
I believe the answer is:
avail
I believe this is a double definition.
'help' is the first definition.
(I know that help can be written as avail)
'benefit' is the second definition.
(I've seen this before)
(Other definitions for avail that I've seen before include "(Of no) use or benefit" , "Be useful" , "Be of value to" , "Be of service to" , "Serve a purpose" .)