Benefit that makes a small number suffer (5)
I believe the answer is:
avail
'benefit' is the definition.
(I've seen this before)
'a small number suffer' is the wordplay.
I cannot really see how this works, but
'a' is found in the answer.
'number' could be 'v' (V is an example) and 'v' is located in the answer.
'suffer' could be 'ail' (ailing is a kind of suffering) and 'ail' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'that makes' acts as a link.
Can you help me to learn more?
(Other definitions for avail that I've seen before include "Make use, take advantage" , "Be of value to" , "Medal (informal)" , "Be useful" , "Serve a purpose" .)