… fine means of securing congregation (5)
I believe the answer is:
flock
'congregation' is the definition.
(flock is a kind of congregation)
'fine means of securing' is the wordplay.
'fine' becomes 'f' (abbreviation).
'means of securing' becomes 'lock'.
'f'+'lock'='FLOCK'
(Other definitions for flock that I've seen before include "A number of sheep" , "Raised-pattern (wallpaper)" , "A company of sheep" , "Congregation" , "Bevy" .)