Lacking purpose, once missing church for example (6,6)
I believe the answer is:
object lesson
'example' is the definition.
(synonyms)
'lacking purpose once missing church' is the wordplay.
I cannot really understand how this works, but
'lacking' could be 'less' (I've seen this in another clue) and 'less' is located in the answer.
'purpose' could be 'object' (I've seen this before) and 'object' is found within the answer.
The remaining letters 'on' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'for' acts as a link.
Can you help me to learn more?
(Other definitions for object lesson that I've seen before include "shows what one should do" , "What may be striking" , "punishment intended as a warning to others?" , "Example typifying a principle" , "Instructive experience" .)