Group of shadowy figures holding church back (7)
I believe the answer is:
species
'group' is the definition.
(eg group of animals)
'shadowy figures holding church back' is the wordplay.
'shadowy figures' becomes 'spies'.
'holding' means one lot of letters goes inside another.
'church' becomes 'ce' (abbreviation for Church of England).
'back' is a reversal indicator.
'ce' back-to-front is 'ec'.
'spies' placed around '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" .)