Appears to be a diocese manuscript (5)
I believe the answer is:
seems
'appears to be' is the definition.
(I've seen this in another clue)
'a diocese manuscript' is the wordplay.
'a diocese' becomes 'see' (I've seen this before).
'manuscript' becomes 'ms' (abbreviation for manuscript).
'see'+'ms'='SEEMS'
(Other definitions for seems that I've seen before include "Appears, looks" , "Gives a certain impression" .)