More safe, more certain around back of church (7)
I believe the answer is:
securer
'more safe' is the definition.
(I've seen this in another clue)
'more certain around back of church' is the wordplay.
'more certain' becomes 'surer' ('sure' can be a synonym of 'certain').
'around' indicates putting letters inside.
'back of' says the letters should be written backwards (I've seen 'backed' mean this).
'church' becomes 'CE' (abbreviation for Church of England).
'ce' backwards is 'ec'.
'surer' going around 'ec' is 'SECURER'.
(Other definitions for securer that I've seen before include "Being safer with rescuer" , "maybe less likely to lose job?" .)