Formality seen in most archbishops (6)
I believe the answer is:
starch
'formality' is the definition.
(I've seen this before)
'in most archbishops' is the wordplay.
'in' indicates the answer is hidden within the clue.
'STARCH' can be found hidden inside 'most archbishops'.
'seen' is the link.
(Other definitions for starch that I've seen before include "Charts (anag) - formality" , "Stiffening preparation used in laundering" , "Stiffening carbohydrate" , "Substance found mainly in potatoes and cereals" , "ceremony" .)