Religious organisation, small and lustrous (6)
I believe the answer is:
satiny
'lustrous' is the definition.
(like satin)
'religious organisation small' is the wordplay.
'religious organisation' becomes 'SA' (abbreviation for Salvation Army).
'small' becomes 'tiny' (similar in meaning).
'sa'+'tiny'='SATINY'
'and' acts as a link.
(Other definitions for satiny that I've seen before include "Silkily smooth" , "smooth result?" , "having a smooth, gleaming surface" , "Smooth and glossy" , "shiny and lustrous" .)