It's so right to be a decent one! (4)
I believe the answer is:
sort
'a decent one' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'it's so right to be' is the wordplay.
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'right' becomes 'r' (common abbreviation).
'to be' is an anagram indicator.
't'+'so'+'r'='tsor'
'tsor' anagrammed gives 'SORT'.
Can you help me to learn more?
(Other definitions for sort that I've seen before include "fashion" , "Work out" , "Separate - kind" , "Type, category" , "Kind, type or make" .)