Most correct, in a fashion, as he should be (6)
I believe the answer is:
rector
'he should be' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'most correct in a fashion' is the wordplay.
'most' means to remove the first letter.
'in a fashion' is an anagram indicator (letters fashioned differently).
'correct' with its initial letter taken away is 'orrect'.
'orrect' with letters rearranged gives 'RECTOR'.
'as' is the link.
Can you help me to learn more?
(Other definitions for rector that I've seen before include "Preacher Man" , "Cleric" , "Head of some colleges" , "Vicar" , "Minister of religion" .)