Formerly working with support of Church (4)
I believe the answer is:
once
'formerly' is the definition.
(I know that formerly can be written as once)
'working with support of church' is the wordplay.
'working' becomes 'on' (on can mean working or activated).
'with support of' is a charade indicator (letters next to each other) (some letters go beneath or support others).
'church' becomes 'CE' (abbreviation for Church of England).
'on'+'ce'='ONCE'
(Other definitions for once that I've seen before include "One-time musical film and song" , "In times past" , "'... bitten, twice shy'" , "Formerly, at one time" , "In days gone by" .)