Senior cleric keeping care of a junior one (6)

I believe the answer is:
deacon
'a junior one' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'senior cleric keeping care of' is the wordplay.
'senior cleric' becomes 'dean'.
'keeping' is an insertion indicator (some letters kept inside).
'care of' becomes 'co' (c/o can mean 'care of' when addressing mail).
'dean' going around 'co' is 'DEACON'.
Can you help me to learn more?
(Other definitions for deacon that I've seen before include "Junior minister" , "Layman attending to church duties" , "Church official - canoed (anag)" , "Clergyman of low rank" , "Minister below a priest" .)
