Do not attend church service when drunk or collection when disorderly (8)
I believe the answer is:
mishmash
'collection when disorderly' is the definition.
(a mishmash is a disordered collection)
'do not attend church service when drunk' is the wordplay.
I cannot really see how this works, but
'when' could be 'as' (eg 'when I walked' means 'as I walked') and 'as' is present in the answer.
This explanation may well be incorrect...
'or' acts as a link.
(Other definitions for mishmash that I've seen before include "Hotchpotch, melange" , "confusion" , "Jumbled mix" , "muddle?" , "A confused mixture" .)