Material displayed by salesman in church (5)
I believe the answer is:
crepe
'material' is the definition.
(crepe is a kind of material)
'salesman in church' is the wordplay.
'salesman' becomes 'rep' (sales representative).
'in' indicates putting letters inside.
'church' becomes 'CE' (abbreviation for Church of England).
'rep' inserted within 'ce' is 'CREPE'.
'displayed by' acts as a link.
(Other definitions for crepe that I've seen before include "One fabric" , "Crinkled paper or fabric" , "Light fabric; pancake" , "Pancake - type of paper" , "Fabric with a wrinkled surface" .)