Head of chapter restricts company for church officer (6)
I believe the answer is:
deacon
'church officer' is the definition.
(deacon is a kind of church officer)
'head of chapter restricts company' is the wordplay.
'head of chapter' becomes 'dean'.
'restricts' is an insertion indicator.
'company' becomes 'co' (abbreviation).
'dean' placed around 'co' is 'DEACON'.
'for' is the link.
(Other definitions for deacon that I've seen before include "Cleric - canoed (anag)" , "Churchman" , "Christian rank below a priest" , "Rank of clergy" , "Church officer" .)