Formerly working with church (4)
I believe the answer is:
once
'formerly' is the definition.
('once' can be a synonym of 'formerly')
'working with church' is the wordplay.
'working' becomes 'on'.
'with' says to put letters next to each other.
'church' becomes 'ce' (abbreviation for Church of England).
'on'+'ce'='ONCE'
(Other definitions for once that I've seen before include "A single time" , "At some former time" , "Cone (anag.)" , "Sometime" , "in bygone era" .)