One helping a superior it's said (7)
I believe the answer is:
abettor
'one helping' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'a superior it's said' is the wordplay.
'superior' becomes 'better' (better is a kind of superior).
'it's said' indicates a 'sounds like' (homophone) clue.
'better' sounds like 'bettor'.
'a'+'bettor'='ABETTOR'
Can you help me to learn more?
(Other definitions for abettor that I've seen before include "One who helps" , "Assistant" , "one to encourage or help" , "One aids another" , "Accomplice" .)