At large empty synagogue, using the facilities at first (2,3,5)
I believe the answer is:
on the loose
'at large' is the definition.
(synonyms)
'empty synagogue using the facilities at first' is the wordplay.
'empty' suggests removing the centre.
'using' becomes 'on' (someone using drugs is 'on' them).
'facilities' becomes 'loo' (euphemistic term for a toilet).
'at first' means one lot of letters go next to another.
'synagogue' with its centre removed is 'se'.
'on'+'the'+'loo'='ontheloo'
'se' after 'ontheloo' is 'ON THE LOOSE'.
(Other definitions for on the loose that I've seen before include "Free from confinement" , "Off the leash" .)