Suppliers of uplift, assuming church provides support (6)
I believe the answer is:
braces
'provides support' is the definition.
'suppliers of uplift assuming church' is the wordplay.
'suppliers of uplift' becomes 'bras'.
'assuming' means one lot of letters goes inside another.
'church' becomes 'ce' (abbreviation for Church of England).
'bras' going around 'ce' is 'BRACES'.
(Other definitions for braces that I've seen before include "Tighten" , "bolsters" , "stays" , "Appliances to correct dental irregularities" , "More than one couple" .)