To no __ (in vain) (5)
I believe the answer is:
avail
(Other definitions for avail that I've seen before include "Be of help or advantage" , "Be useful" , "Use to one's advantage" , "See 3" , "Make use, take advantage" .)
I believe the answer is:
avail
(Other definitions for avail that I've seen before include "Be of help or advantage" , "Be useful" , "Use to one's advantage" , "See 3" , "Make use, take advantage" .)