Church gathered to welcome new material (6)
I believe the answer is:
cement
'material' is the definition.
(cement is a kind of material)
'church gathered to welcome new' is the wordplay.
'church' becomes 'CE' (abbreviation for Church of England).
'gathered' becomes 'met' ('meet' can be a synonym of 'gather').
'to welcome' is an insertion indicator (inserted letters are welcomed in).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'met' placed around 'n' is 'ment'.
'ce'+'ment'='CEMENT'
(Other definitions for cement that I've seen before include "Stick together - substance used by a builder" , "It hardens when wetted" , "Bind firmly" , "It hardens when water is added" , "Seal; bonding agent" .)