One who prays is good, good adult, right? (6)
I believe the answer is:
beggar
'one who prays' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'is good good adult right?' is the wordplay.
'is' becomes 'be'.
'good' becomes 'g' (abbreviation).
'good' becomes 'g' (abbreviation).
'adult' becomes 'a' (abbreviation).
'right?' becomes 'r' (common abbreviation).
'be'+'g'+'g'+'a'+'r'='BEGGAR'
Can you help me to learn more?
(Other definitions for beggar that I've seen before include "One may entreat you" , "One pleading desperately" , "One importuning" , "One who can't be a chooser?" , "Person who can't choose?" .)