Group of shadowy figures holding church back (7)
I believe the answer is:
species
'group' is the definition.
(species is a kind of group)
'shadowy figures holding church back' is the wordplay.
'shadowy figures' becomes 'spies'.
'holding' is an insertion indicator.
'church' becomes 'ce' (abbreviation for Church of England).
'back' says the letters should be written backwards.
'ce' written backwards gives 'ec'.
'spies' enclosing 'ec' is 'SPECIES'.
'of' is the link.
(Other definitions for species that I've seen before include "Group of organisms" , "Kind of creature" , "Kind, sort" , "Variety, taxonomic group" , "Biological group" .)