Rustic forbidden to appear in a French church (7)
I believe the answer is:
Here is my best explanation:
'rustic' is the definition.
'forbidden to appear in a french church' is the subsidiary indication.
'forbidden' becomes 'out' ('out' can be a synonym of 'forbidden').
'to appear in' is an insertion indicator.
'a french' becomes 'un' ('a' transated into the French language).
'church' becomes 'ch' (common abbreviation).
'out' put into 'unch' is 'uncouth'.
(Other definitions for uncouth that I've seen before include "Crude", "Ill-bred, unrefined", "Uncultured", "Gross", "Loutish", "Oafish", "Vulgar and coarse", "Ill-mannered", "Unrefined" and "lacking in charm".)