Manuscript has section about church people (9)
I believe the answer is:
parchment
'manuscript' is the definition.
(thesaurus)
'section about church people' is the wordplay.
'section' becomes 'part' (synonyms).
'about' means one lot of letters goes inside another.
'church' becomes 'ch' (common abbreviation).
'people' becomes 'men' (men are people).
'ch'+'men'='chmen'
'part' placed around 'chmen' is 'PARCHMENT'.
'has' acts as a link.
(Other definitions for parchment that I've seen before include "Skin prepared for writing on" , "Paper made from animal skin" , "High-quality paper" , "diploma" , "Work on skin" .)